Hi,
i am trying to check how long it takes to read files from sd card.

i create 100 files 10k each

for(i = 0;i<100;i++)
{
wsprintf(wszBuf, _T("%s\\Filetest_%d.txt"), g_szVolume, i);
RETAILMSG( 1, ( wszBuf ) );
RETAILMSG( 1, ( _T("\r\n") ) );

hFile = CreateFile(wszBuf, GENERIC_WRITE|GENERIC_READ, 0, NULL, CREATE_ALWAYS, 0, 0);
WriteFile(hFile, filedata, dwFileSize, &dwBytesWritten, NULL);
CloseHandle(hFile);
}
//end create file

dwStartTick = GetTickCount(); //Get initial tick count


//We are going to Open/Close the file for every file read.
for (i=0; i<dwInterval; i++)
{

wsprintf(wszBuf, _T("%s\\Filetest_%d.txt"), g_szVolume, i);
RETAILMSG( 1, ( wszBuf ) );
RETAILMSG( 1, ( _T("\r\n") ) );

hFile = CreateFile(wszBuf, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, 0);

if(!ReadFile(hFile, &filedata_readed, dwFileSize, &dwBytesWritten, NULL))
{
ShowLastError();
return(0);
}

CloseHandle(hFile);
}
dwEndTick = GetTickCount();

}

is it right way to do that?

How can i open directory and to get list of all files?

You have to see how precise you want the results to be.
For this code to give you precise results you'll need to
keep your system free. Like if your system is also doing
some heavy processing simultaneously then the results will
show you that. May be thats what you want in which case its
ok.
In any case you may want to make it into a critical section.
To make your time span calculation more precise you can explore
the use of QueryPerformanceCounter and QueryPerformanceFrequency.

Use FindFirstFile, FineNextFile to get files in a directory.

Regards
Ankur