Question : Problem: Reformat Harddrive

The computer hard drive has had many infections and now runs very slowly.  I am going to reformat the hard drive and reinstall Windows XP Pro.  Should I use something like WipeDrive
http://www.whitecanyon.com/wipedrive-erase-hard-drive.php to make sure all infections (viruses, Malware etc) are cleaned.

Answer : Problem: Reformat Harddrive

no, you don't need to.
while re-installing XP, just erase the partition(s) then re-create it and reformat it (not quick format).

hope it helps.