Rundll32 is used by windows to run various functions in DLL's as needed. Nearly everything relies on Rundll32, all the control panel applets, display properties, etc. etc. etc. As far as the problem, I'd agree with Norm, try to reseat all of the cards. If that doesn't work, I'd try just completely formating the drive and reinstalling clean. If all else fails, throw some ram in there and install Win2K
Oh, and for the S3 (Trio and onboard I assume) adapter, I doubt it, but it could conflict. Disable the S3 adapter in device manager if you can't find a way in the BIOS or a jumper on the motherboards to completely disable it and see what happens.