It's hard to say, but the computer might be infected with viruses. Something must have corrupted that critical OS file. I'd try copying that file from the Windows installation CD and doing some anti-virus checking. If that doesn't work, it may be time to re-format the hard drive.

__________________
2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL