Any idea which ones? Some are much harder to get rid of than others.
Welcome to TechIMO, BTW.
If it IS a virus problem, then you may need to do a virus scan of the MBR as well as the drive partition, so use a known clean boot floppy or a bootable CD with an antivirus scanner on it. even that is not infallible, as it will depend on how up-to-date virus definitions on the floppy/CD are.
I'd suggest wiping the whole partition with fdisk, re partitioning, and reinstalled the ghosted image.
If it worked before, unless you were using a DDO or something, then it should work again.
Cheers
Mick