http://www.f-prot.com/products/corporate_users/dos/
Download here:
http://www.f-prot.com/download/download_fpdos.html
Definitions update:
http://www.f-prot.com/cgi-bin/get_randomly?fp-def
http://www.f-prot.com/cgi-bin/get_randomly?macrdef2
Instructions for running off floppies:
http://www.f-prot.com/support/fpdos_faq/06.html
I know it says F-Prot Antivirus for DOS will run under Windows 3.x, Windows 95, 98, OS2, or UNIX, LINUX or Macintosh workstation running a DOS or Windows emulator - but it does run on Win2000 at a command prompt and I assume it will run on XP.