Reinstall windows every 6 months? That's crazy talk.
Get a GHOST type of program. With that you build the perfectly optomized install of windows and even any programs you want, get all your drivers and everything installed just right and then use Norton Ghost or some other similar program that takes a snapshot of your hard drive and stores it on a different drive or DVD.
Then all you have to do when you want to clear your system and reset back to perfection is restore that image you have saved somewhere. it only takes like 10 minutes to restore and your computer is back to perfection.
So after surfing porn and hunting for warez serial numbers and your system is loaded up with crap spyware and such you just image your puter back.
...and of course keep your importatnt files on another drive so they don't get overwritten. I couldn't live without it. Best thing since sliced bread.