|The bios sees physical hard drives; not the partitions on them. A hard drive can have more than one partition and therefore more than one drive letter. That is determined by how the drive is set up when you perform the installation. It's not determined by the bios.|
To reinstall XP you can boot from a restore disk (if you have one) or a restore partition on the hard drive (if there is one) or from a regular XP installation disk.
When booting from a restore disk or restore partition you need to follow the screen prompts to do the reinstall.
When booting from a regular XP disk you choose to do the install. One of the steps in that process will allow you to delete the current XP partition. You'd do that and then it'll ask where to do the installation and you'll choose to use the now unpartitioned space. It'll partition and format it and start the installation.
But if you're sure you have a virus have you tried to remove it? You might try something like Malwarebytes. You can download the free version here:
If your computer is just running slow and you're assuming it's a virus, well maybe it's not. Computers will slow down if you have too much stuff running in the background. Or maybe you need more ram. 512 meg isn't very much by todays standards.
Real men don't use AntiVirus; they just reformat