Dilema is wether to bother with AniVirus software, seems to create more problems than it tries to solve.
That depends very much on what AV software you use, and...
By its very nature it must sit in the registrys and at the root of the operating system always running in the background.
Not necessarily... on the Windoze 98SE system that I have at home, for use on those occasions when somebody
insists on sending me a Word/Excel/PP document and won't provide it any other way

, I have a copy of Sophos, with Intercheck, (their on-access virus sweeping)
turned off -- that's the important bit. I would hope that
any decent AV software would allow you to do this. I save the file, and run the virus scanner, in on demand mode, across the file. Picks up every virus-infected document I've been sent, and doesn't interfere with the OS. I have no reason to suppose that this wouldn't work with XP. Requires discipline on the part of the user, of course...