will allow you to do a full recovery.

That's the nuclear option - nuke the hard drive and start fresh. If you want to be more surgical, you can try running ccleaner. It will clean up a lot of the crap, optimize the registry, etc. It might be enough to restore the performance and save the hassle of reinstalling everything.

If that doesn't work, wipe and reload. For the record, I typically reinstall Windows once a year just because Windows has a tendency to bloat.