Need help with ... Virus or somthing else.

Hi, I just recently bought a new system, (specs below). And I have tried everything I can think of to get it running. The errors it give's me are fairly widespread, useualy dealing with not being able to find files, or errors installing new files etc. They occur on CD to HD installs, Internet to HD downloads/Windows updates. But never on OS installs, (Windows 2000). When I try to install Linux everything seems to work fine, But I'm not very familer with Linux so hard to say. On ocasion I get a "somefile.dll cannot be located" Error on win2k's boot sequence, and When I get those, the system will not boot at all, Safe mode or otherwise I've tried the Win2k version of "fixmbr" and "fixboot" But they don't seem to have any effect. I downloaded 3 different Anti Virus programs and they all give a clean bill of health. (Norton, PC Cillin, And Panda). All of the hardware/cables are brand new, Excepting my Video Card, Sound card and CD rom.

System specs as follows:

MSI KT3 Ultra2 Motherboard
AMD 1800XP CPU
512 MB PC2100 DDR ram
3d Prophet Radeon 8500LE (128mb)
IBM Deskstar 40GB 7200 RPM drive
SB Live! sound card.
I've tried 2 different CD drives, Ones a Creative CDRW and the other a fairly Old CD Racer CDRW.

If anyone has any ideas or opinions please let me know

TIA.

Scott