I have created a page to insert new data into my database but when i try to insert it i get this error message: "Object reference not set to an instance of an object.", does any one have any ideas?
Thanks for you time,

Show us the code.

here's the code

<%@ Page Language="c#" Debug="True" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.OleDb" %>
<script runat="server">

    OleDbConnection objConnection;

    private void Page_Load(object sender, System.EventArgs e)
    {
    OleDbConnection objConnection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; data source=AAC.mbd");
    }

    private void btnInsert_Click(object sender, System.EventArgs e)
    {
    if (Page.IsValid)
    {
    String strSQL = "INSERT INTO Computers (Location, User, TypeOfComputer, Manufacturer, ModelNumber, SerialNumber, DatePurchased, DateGarunteed, DateMaintenence, CPU, Memory, HardDrive, CDROM, SoundCard, VideoCard, NetworkID, PrinterType, OtherEquipment, OS, ApplicationSoftware, NetworkCard, NetworkConnection, Update) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
    OleDbCommand dbComm = new OleDbCommand(strSQL, objConnection);
    dbComm.Parameters.Add("Location", OleDbType.VarChar, 32, "Location");
    dbComm.Parameters.Add("User", OleDbType.VarChar, 32, "User");
    dbComm.Parameters.Add("TypeOfComputer", OleDbType.VarChar, 32, "TypeOfComputer");
    dbComm.Parameters.Add("Manufacturer", OleDbType.VarChar, 32, "Manufacturer");
    dbComm.Parameters.Add("ModelNumber", OleDbType.VarChar, 32, "ModelNumber");
    dbComm.Parameters.Add("SerialNumber", OleDbType.VarChar, 32, "SerialNumber");
    dbComm.Parameters.Add("DatePurchased", OleDbType.VarChar, 32, "DatePurchased");
    dbComm.Parameters.Add("DateGarunteed", OleDbType.VarChar, 32, "DateGarunteed");
    dbComm.Parameters.Add("DateMaintenence", OleDbType.VarChar, 32, "DateMaintenence");
    dbComm.Parameters.Add("CPU", OleDbType.VarChar, 32, "CPU");
    dbComm.Parameters.Add("Memory", OleDbType.VarChar, 32, "Memory");
    dbComm.Parameters.Add("HardDrive", OleDbType.VarChar, 32, "HardDrive");
    dbComm.Parameters.Add("CDROM", OleDbType.VarChar, 32, "CDROM");
    dbComm.Parameters.Add("SoundCard", OleDbType.VarChar, 32, "SoundCard");
    dbComm.Parameters.Add("VideoCard", OleDbType.VarChar, 32, "VideoCard");
    dbComm.Parameters.Add("NetworkID", OleDbType.VarChar, 32, "NetworkID");
    dbComm.Parameters.Add("PrinterType", OleDbType.VarChar, 32, "PrinterType");
    dbComm.Parameters.Add("OtherEquipment", OleDbType.VarChar, 32, "OtherEquipment");
    dbComm.Parameters.Add("OS", OleDbType.VarChar, 32, "OS");
    dbComm.Parameters.Add("ApplicationSoftware", OleDbType.VarChar, 32, "ApplicationSoftware");
    dbComm.Parameters.Add("NetworkCard", OleDbType.VarChar, 32, "NetworkCard");
    dbComm.Parameters.Add("NetworkConnection", OleDbType.VarChar, 32, "NetworkConnection");
    dbComm.Parameters.Add("Update", OleDbType.VarChar, 32, "Update");
    dbComm.Parameters["Location"].Value = txtLocation.Text;
    dbComm.Parameters["User"].Value = txtUser.Text;
    dbComm.Parameters["TypeOfComputer"].Value = txtTypeOfComputer.Text;
    dbComm.Parameters["Manufacturer"].Value = txtManufacturer.Text;
    dbComm.Parameters["ModelNumber"].Value = txtModelNumber.Text;
    dbComm.Parameters["SerialNumber"].Value = txtSerialNumber.Text;
    dbComm.Parameters["DatePurchased"].Value = txtDatePurchased.Text;
    dbComm.Parameters["DateGarunteed"].Value = txtDateGarunteed.Text;
    dbComm.Parameters["DateMaintenence"].Value = txtDateMaintenence.Text;
    dbComm.Parameters["CPU"].Value = txtCPU.Text;
    dbComm.Parameters["Memory"].Value = txtMemory.Text;
    dbComm.Parameters["HardDrive"].Value = txtHardDrive.Text;
    dbComm.Parameters["CDROM"].Value = txtCDROM.Text;
    dbComm.Parameters["SoundCard"].Value = txtSoundCard.Text;
    dbComm.Parameters["VideoCard"].Value = txtVideoCard.Text;
    dbComm.Parameters["NetworkID"].Value = txtNetworkID.Text;
    dbComm.Parameters["PrinterType"].Value = txtPrinterType.Text;
    dbComm.Parameters["OtherEquipment"].Value = txtOtherEquipment.Text;
    dbComm.Parameters["OS"].Value = txtOS.Text;
    dbComm.Parameters["ApplicationSoftware"].Value = txtApplicationSoftware.Text;
    dbComm.Parameters["NetworkCard"].Value = txtNetworkCard.Text;
    dbComm.Parameters["NetworkConnection"].Value = txtNetworkConnection.Text;
    dbComm.Parameters["Update"].Value = txtUpdate.Text;

    int iID = 0;
    try
    {
    objConnection.Open();
    dbComm.ExecuteNonQuery();
    }
    catch (Exception ex)
    {
    Response.Write(ex.Message);
    Response.End();
    }
    finally
    {
    if (objConnection.State == ConnectionState.Open);
    objConnection.Close();
    }

    Response.Write("A new record has been added");
    Response.End();
    }
    }

</script>
<html>
<head>
    <title>Validating a Feild</title>
</head>
<body>
    <form id="Form1" methode="post" runat="server">
        <table id="Table1" style="Z-INDEX: 101; LEFT: 8px; POSITION: absolute; TOP: 8px" cellspacing="0" cellpadding="0" width="300" border="0">
            <tbody>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label1" runat="server">Location</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtLocation" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label2" runat="server">User</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtUser" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label3" runat="server">Type of Computer</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtTypeOfComputer" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label4" runat="server">Manufacturer</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtManufacturer" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label5" runat="server">Model Number</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtModelNumber" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label6" runat="server">Serial Number</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtSerialNumber" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label7" runat="server">Date Purchased</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtDatePurchased" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label8" runat="server">Date Garuntee Expires</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtDateGarunteed" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label9" runat="server">Date Maintenence Contract Renewal</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtDateMaintenence" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label10" runat="server">CPU</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtCPU" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label11" runat="server">Memory</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtMemory" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label12" runat="server">HardDrive</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtHardDrive" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label13" runat="server">CD-ROM</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtCDROM" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label14" runat="server">SoundCard</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtSoundCard" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label15" runat="server">VideoCard</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtVideoCard" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label16" runat="server">NetworkID</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtNetworkID" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label17" runat="server">Printer Type</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtPrinterType" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label18" runat="server">Other Equipment</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtOtherEquipment" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label19" runat="server">OS</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtOS" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label20" runat="server">Application Software</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtApplicationSoftware" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label21" runat="server">Network Card</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtNetworkCard" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label22" runat="server">Network Connection</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtNetworkConnection" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px">
                        <asp:Label id="Label23" runat="server">Update</asp:Label></td>
                    <td>
                        <asp:TextBox id="txtUpdate" runat="server" width="193"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td style="WIDTH: 115px" colspan="2">
                        <asp:Button id="btnInsert" onclick="btnInsert_Click" runat="server" width="298px" Height="27px" text="INSERT!"></asp:Button>
                    </td>
                </tr>
            </tbody>
        </table>
    </form>
</body>
</html>

You have redeclared objConnection variable into Page_Load proc in the initialization statement, and initialization affects only into Page_Load proc's scope. You have to remove OleDbConnection declaration keyword in Page_Load proc.

...but the Soon is eclipsed by the Moon

ok, thank you that worked
but now i'm having a problem with my insert statement
error message: "Syntax error in INSERT INTO statement."
can you help?

Well,
I see that one field in your table named "Update". This is a keyword, and it is possible that this name is responsible for INSERT INTO error (maybe there are more error sources). You should avoid all names similar to some keywords. Some applications allow you to use them, but generally it is recommended to avoid them.

...but the Soon is eclipsed by the Moon

Ok i made that change but i'm still getting the same error

Hmm... I think that "User" can be problematical, too. Try to play with some suspicious words used for field names...

...but the Soon is eclipsed by the Moon

i tried to change User so that it wouldn't be problematic, so i changed it to UserName and replaced User with UserName throught the code but now when i try and insert data i get this message "The INSERT INTO statement contains the following unknown field name: 'UserName'. Make sure you have typed the name correctly, and try the operation again.", i've looked throught the code many times makeing sure i had spelled it right but i can't seem to figure it out, i also changed the field name in my database to UserName, do you have any idea and will using UserName instead of USer fix the problem with keywords?

I tested particularly Update and User keywords, and I found that both words are problematical. I have replaced Update with Update1 and User with User1 (in the SQL statement and table structure, of course), and code worked OK.

...but the Soon is eclipsed by the Moon