windows 2000 how to completely restore/replace registry

[holden j caufield]

hi I was wondering if there was a way to complete restore/replace the registry in windows 2000. Now I can get to safe mode and and such and I've got my complete .reg file and when I try to merge it in safe mode it says some keys could not be replaced because they were in use. Now in 98 the whole scanreg and restore option before you hit the OS. Is there such an option in NT. thanks