1st off I don't know of any viruses out there that will cause your files to become corrupt. That doesn't mean they don't exist, but it is very rare. If the files are truly corrupt I would run some diagnostics on the drive itself as it may be the source of the problem.
2nd be careful about installing a drive in your PC that you suspect is infected with a virus as if it is a boot sector virus - you could infect your pc.
Now if the drive is good, and you want to format and reinstall windows you will need to boot to the installation CDROM. Go into the BIOS setup and find the setting that controls the boot order. (Usually in the Boot or Advanced menu) change the order to CDROM 1st. Insert the install disk and save and exit the BIOS. When prompted, hit a key to boot from the CDROM. After hitting F8 to accept the license agreement, you will be given the choice to repair and current install or perform a new install. Choose new and when prompted on where to install delete and then recreate the primary partition. XP will automatically reformat the partition before installing.
Ok, this next part I'm a little sketchy on as I've never had to use it. So if someone knows any different feel free to correct me.
If XP does not find the drive, it may be that your master boot record is infected or corrupted. In that case abort the installation and reboot to the install disk, but this time choose r to use the system recovery console. at the command prompt type fdisk /mbr which should restore the master boot record.