..there's no way to know whether the "good" files will correctly overwrite the bad ones.. And because counterfeit copies can frequently contain other "bad" stuff which will cause damage and aren't really part of the operating system, you can be sure those items also won't get removed.
Your best bet.. Make backups of your important files, then format the drive and install XP plus all the drivers for all your hardware devices.. That way, you KNOW you've got a good, clean installation.
Hope this helps.
I am running xp pro ,but it is a counterfeit copy, I have just bought microsoft xp pro upgrade with service pack 2,this is a genuine copy, will this load over my existing copy,and will I retain or lose my stored data. Regards Pierre..