Worth a try.....
Boot while tapping away on the F8 key before Windows itself starts to load.
You will stop at a DOS screen of alternatives.
Choose (5?) Comand prompt only.
When the cursor changes to C:> type...
exactly like that with a space after scanreg.
You will then have a list of dates when the computer ran successfuly. Choose one which is before the current mess, and follow the prompts.
This will restore the registry only but it has to be tried.