take the internal hard drive out and use a working computer to clean it from the virus's
Not a good idea, because you may infect other computer.
It's better to download antimalware programs on good computer, burn them to CD, and install them on bad computer from CD.
how do i fix the registry of NEWLY CLEANED HARD DRIVE
It depends what kind of damage was done. If it's a damage from virus itself, it may be fixed by running proper antimalware tools.