There was a way to pull back up registry files out of somewhere... think system restore points... using the recovery console. and restore them. IF system restore didn't work for some reason. Your question is extremely vague though.
Modern versions of Windows backup the registry (and other files) regularly at startup (once a day)
'Last known good' restores the latest version but that may not rectify the problem and you may need to go further back before the registry got corrupted
There is a Howto at Microsoft expaining the proceedure.
You need to be able to type accurately and have access to the admin account password (if set) when using the emergency command console.
An alternative utility is provided in the ubcd4win project (www.ubcd4win.com) which lets you browse the list of backups and select the one you want, it then backs up existing registry files then copies (and renames) the backup registry files to the correct location. [c:\windows\system32\config\]
Utility is called 'Registry Restore Wizard'
You need a Win XP or Win 2003 CD to build the ubcd4win project