Fran,

A virus is not going to physically harm your hard disk in such a way that you would need to replace it.

Viruses impact only the software installed on your machine and software can be fixed.

Your disk may have bad sectors, probably because it's wearing out. Before replacing the hard drive, I would use malwarebytes, then windows disk check. If you still have problems and can't boot to windows, then perhaps a fresh install will work. If after all that and your computer is not running correct, then a new hard drive is the answer.

Then again, hard drives are cheap, and you may just want to start with a brand new one...or a new computer. Windows 7 is awesome, and IMO as good as a MAC, at a much much lower price