XP Forever!!
I will continue to use it. In fact, I installed a fresh version on a spare hard drive and downloaded all the updates from Windows Update so I can clone a drive with all the latest updates in case I need to re-install it. But seeing as how I have been cruising with no problems for YEARS now on the last install, that may not be necessary. I will probably download some anti-virus freeware at some point, just for the heck of it.
How's this for a conspiracy theory: MS unleashes an unstoppable virus that only infects XP machines to force an upgrade to 7 or 8. Let's face it, Bill Gates will never be rich enough.