Try correcting the registry first, and you can go back before the problem if it hasn't gone beyond the 5 day limit, if you can't resolve it by attempting to run the System File Checker, but on an outside chance try unplugging the mouse and plugging it back in,( you can reverse the mouse and key board and cause all kinds of error messages in some circumstances) If it fails , then here are the registry tools needed to correct it , the last one to use is the Go Back function;
scanreg /restore (Goback feature up to 5 days )
scanreg /opt (Optomize registry by defrag and eleminating orphans )
scanreg /fix (Uses current settings and restores them to operational )
I would use the sequence of /fix, then /Opt , and if all else fails and you areout of time you can revert to the way it was if not too much time has elapsed by using the /restore , all are done from the Dos prompt. Luck