Try a program called regcleaner found
here after opening the program, close it and open it again (you must not skip this step) You only need to do it the first time you run the program. Then go to "tools", "registry cleanup", "do them all". It will scan your reg for any invalid files and give you the option to delete them. I have always deleted them all and never had a problem. By the way, it does create a backup so you can restore back if needed. I also use crap cleaner as ethel suggested to you, it is also a great program that ive been using for a long time but it does not find everything. Between ccleaner and regcleaner you should be in good shape.