It does matter. Windows: 47,000 viruses. Mac (not counting Word macro viruses): 40 viruses. Unix: Don't know but it's not much. You can see the difference in the raw numbers; and it's not because of popularity, but the exploits MS introduces for their own purposes. ("Oh, that's in there? Here's a patch.") MS's Allchin was quoted as saying 'security is a good reason to upgrade (to Win 2K)'. Fact is the MS campus has migrated to Win 2K and they went down. Besides, viruses serve a useful purpose: culling the herd of the weak and lame.