As a last resort, try running crap cleaner, which you can get at www.download.com.  Do a search for crap cleaner.  It will clean up the registry and show problems and fix them.

A word of warning tho, if the registry is really fubar, it might cause other problems.  But before you restore your whole system and reinstall windows, you might want to give that a shot.

Also, make sure to do a scan disk, as I was having a slow painfully timed out load until i realized I hadn't done a scandisk in eons.