Help! XP chain problems!

Hey everyone!

I'm new here and I was hoping someone can help me with my problem. I'm running windows xp pro and all of a sudden, it wouldn't boot up anymore. BSOD came up saying there was a corrupted registry file. I used another hard drive to access this drive and replaced some files in my system32/ config with some older ones from my repair folder from the windows folder. Some of my programs will not work now and I can't find the latest system restore point. I don't think I had one. The newer file's dates were somewhere in January while the older ones were some where in November and a lot has changed since then. Is this the cause of my programs not working? How can i fix this? If you feel that I'm not giving enough information, please ask.
Thanks a lot!