hard drive issues

[johnnybeef]

ok ok i know this isnt a computer forum, but this is the closest thing i know of. I caught a trojan horse that i cant get rid of by any means besides reformating my hard drive. i do have a hard copy of windows xp pro, but when i put it into the drive, it said i couldn't install because i have a newer version of windows on my computer. what do i need to do to completely wipe out my hard drive and reinstall windows. if it helps, i do have 2 hard drives.