In the spirit of full disclosure, I run Windows 98 on all of my computers except for one which uses Windows 2000 Pro for the sake of LabView and a IEEE-488 ([G/H]PIB) bus.

Windows is the most common virus vector because it is the most common OS. The virus writers get the most bang for their buck by attacking Windows. I'll bet real money that if those of you running *nix ever succeed in your quest to switch the world to your OS, then we'll find out just how vulnerable your systems are. If anything appears to be foolproof, it's because there aren't enough fools fooling with it.

And if you believe that Outlook is the problem, read "The Cuckoo's Egg." Can anyone say GNU EMACS? Note also that this event predated Windows (and maybe even DOS!?).

And there's my two cents worth.