Really? I've never had a virus on any of my computers. Even if I did, a fresh install of Windows fixes everything.
I'm not sure why you bought six computers.
Yes a clean windows reinstall removes any viruses (you might have some infected programs so run a virus scan before starting them).
1.5 years ago I had a serious virus infection, Installed windows 2008 server on a disk, OS did not find network card and I had to add it later, for some reason the firewall was not activated on the card and I did not install antivirus at once as I had to get it from work, (servers demand special antivirus) in that time I got multiple viruses who also infected my xp harddrive.
Win xp continued to have problems so I installed win 7.
Win 7 did not run Fallout 3 and Oblivion for some reason, so I put my old core2 system in a new case and sold it, bought a six core amd processor, 8GB ram, a ssd disk and a ati 5770.
Upside is that my system should be Skyrim ready.