[dba-Tech] Win2000 dual boot, but how do you edit the registry?

I have a PC (AMD2600 DFI NF2 Ultra (rev a)) that I attempted to upgrade 
to sp4 but failed miserably...

I say failed, because immediatly after the install of sp4, it rebooted 
and that windows 2000 profile hasn't worked since.

I re-installed windows2000 to a new directory w2kpro and that has booted 
fine, but how do I edit the registry for the first system, or better yet 
uninstall sp4?

Thanks,

-- 
-Francisco