I have an Atari 800XL and a handful of games for it, I guess that's the oldest thing I've got going. Admittedly, it's a lot more integrated and less likely to die than an old desktop PC tends to be.
As for Viruses, I think even if one worked their butt off and got it going (it can be done with Win 3.1, but web browsing is nearly broken with modern sites .. I think Netscape 3.x or some such nonsense was the last 3.x browser more or less) .. I doubt any common current virus would actually be able to do anything. They're all designed to attack XP for the most part, and a good number attack Vista/7 (and presumably 8). Running 3.x is probably about as safe as using a Mac, just a lot less capable. This is ignoring the possibility of running into an infected floppy or something that hadn't been used in years. Really old viruses seem to stop being propogated after a while. How long has it been since anyone has seen a blaster infection in person? I hadn't in at least 4-5 years, possibly longer, and was refurbing a donated laptop for someone and when I booted it, LOL BLASTER. Must have been too expensive for whomever to fix, so they tossed it in a box and ignored it for years.