Reinstalling XP, need help

I have to reinstall XP Pro because an appearently unknown virus has infected my computer.

I'm not sure if I need to formate my C: drive first and if so how should I go about doing that.

I have attempted to reinstall XP Pro and in the begining of the install it copies all the install files and then restarts my PC. I then get an option to restart using windows XP pro or Windows XP Pro Setup. XP Setup is default so I let it do that but then I get a black screen with a flashing underscore. It's been 30 mins. The computer has not made a sound and has not gone further.

Now what?

Help!!!

 

http://www.tweakhound.com/xp/installxp/installXP1.htm
This is a bit dated, but relevant. If you can download SP2 and SP3 and copy to external media (CD, external drive) then do so beforehand, Your install CD may already have SP2. I believe you are using an XP installation CD and not a System/Factory Restore CD. You should put the CD in the drive and then restart the computer, if it doesn't boot from the CD, but boots from the hard drive you already have WIndows installed on, then you need to get into the BIOS and change your boot order putting you CD/DVD drive first. Enter BIOS usually done by tapping F1, F2, or delete key as computer is starting.
http://www.kellys-korner-xp.com/xp_bios.htm
Hope this is of some assistancerolleyes, installing XP gets easier every time you do it:-D.

 

Thanks I did this but I just get a black screen with a flashing Underscore on the screen.