all critical data and do a clean install with a valid copy. Or you can try an in place repair installation, installing the valid copy over the bogus one.
Is it possible to buy a copy of genuine windows or a valid cd key and use the valid cd key to make windows genuine(without losing data)? A friend wasn't aware that a so-called 'tech shop' put a bootleg copy of the software on his machine when he took it in and now wants to fix the issue without losing his files. Any help is appreciated!