OK, thats not good. You have deleted a registry hive. You should never replace only one perty of the registry. Many registry keys are really sub-keys in another key. So, since there is a connectivity if you replace one the replace all to maintain that unity. After the pain is reduced try this:
How to recover from a corrupted registry that prevents Windows XP from starting
http://support.microsoft.com/?kbid=307545
This is a complex procedure so print the page and check off each completed item. Set aside enough time to not have to stop half way through. I have used this many times with great success. That said I use System restore from the Winternals ERD commander most the time now.
http://www.winternals.com
Good Luck,
razz