Registry Backup recovery on external disk

My computer A was unable to restart after CCleaner "cleaned" the registry. I had to take out the disk in order to recover the original registry running on computer B. How do I merge the backuped registry file in the external HD (USB) to replace the existing registry only on the disk? Thanks

Very strange. First off did you try safe mode?

If safe mode wont work, what about fixboot and fixmbr in the emergency console?

No way to restart even in Save Mode and all other options under F8. My problem is to find the way to remerge the old registry values into the files in the disk manually, but the backup file is only one file and in the config registry directory there are 6 files. Do you know how to merge them manually? The backuped file is 74 MB big and the ccleaned is 34 MB (6 files together)