There are numerous threads on this and many ways of dealing with it,. but the best is System Restore to before it all happened. If that can't be accessed in regular mode perhaps it can be initiated in Safe Mode - reached by tapping F8 repeatedly while booting up.
Then go to Start and type rstrui in the search box. Rstrui.exe should appear in the window above and simply click that and OK any prompts.
Try that for a start. It sometimes takes a while to open by the way.