I have a problem and here's the problem

I receive this message after I have restarted my PC.
Windows could not start because the following file is missing or corrupt:
\WINDOWS\SYSTEM32\CONFIG\SYSTEM
You can attempt to repair this file by restarting Windows Setup using the original Setup CD-ROM.
Select 'r' at the first screen to start repair
There was no problem after I have done all that I was told until I got myself in the Windows (XP) Setup. I pressed 'r' and it will eventually bring you back to MS-DOS again. And here's what it says in white text:
Microsoft Windows XP (TM) Recovery Console.
The Recovery Console provides system repair and recovery functionality.
Type "EXIT" to quit the Recovery Console and restart the computer.
1:C:\WINDOWS
Which Windows installation would you like to log onto (to cancel, press ENTER)? I type '1' of my choosing and then ENTER. And here's what I get after that.. C:\WINDOWS>
What happens after that? But how can I repair the problem? It's manual and how am I suppose to correct that?

Please, I just need the commands to repair my "WINDOWS\SYSTEM32\CONFIG\SYSTEM" back.
I'm thinking of installing my Win XP back but then it says, it will eventually overwrite my \Windows; all subfolders, applications, security, My Documents and so on. But would it also delete my programs installed in C: drive? Or just overwritten in \WINDOWS folder.
Please I need help! I really need someone who really knows about this one. Which ones are okay for me: install my XP back or just repair the specific problem?
All help will be much appreciated and thank you in super advance