It does sound like some misconfiguration due to many programs being installed/uninstalled etc.. registry must be a mess... a backup of data then format would be recommended...

I agree that regular formats are good... but 6months (for most people) is too quick... i try to do it 1 or 2 years (more to reset AV licenses), but with only 1 computer, trying to backup 200GB of music/movies/photos and files... is a major pain! Dont get me started on drivers...argh!