Really, the easy answer is to use Visual Studio 2005 for ASP.NET 2.0
You *CAN* use VS2008 and ask it to target 2.0, but I think you will find it easier to just us VS2005.
You can use the FREE version of "Visual Web Developer Express 2005" and that will produce ASP.NET 2.0 code. Needless to say, VS2005 use VB2005.
.NET is the "generic" name for VB2002, VB2003, VB2005, and VB2008 (and future versions). VB6 is old and you should ignore it completely.