I rebuilt my Windows XP system yesterday, as a developer I find myself installing, patching, unistalling software frequently and find at max every six months I need to cleanout my pc to solve performance issues. I installed XP SP1 from my install media and after install and applying service pack 2 the damn thing bluscreened while performing a Windows Update. Thats a record for me.
If I had the money I'd move to Mac for personal use as the problems with Windows systems really begin to wear thin after a time. IMHO it boils down to the fact that with Mac, all the hardware is chosen specifically for the OS so there aren't any support and maintenance issues, everything just works so you pay a premium for it. With Windows the OS has to try to support every possible combination of hardware permissible so it's little wonder that there will be issues and vulnerabilities.
And Macs are shiny