I guess I'm the desenting vote.
Reinstallation should be a last resort. There are several things to try first.
Uninstall any unused apps on your hard drive, for starters.
Clean up your registry. Try TweakNow (http://www.majorgeeks.com/TweakNow_R...ner_d4134.html
Defrag your hard drive.
Use the System Configuration Utility to speed up your system and your start-ups. Click Start, Run, 'msconfig', Startup tab. Uncheck everything but what you absolutely must have (firewall, AV, graphics drivers, whatever). Click Apply, OK, and reboot. A grey box will pop up on startup. Check the Do Not Run on Startup and you're in business.
Try those and see if it doesn't help out your rig.