System recovery in Windows XP

If Windows XP wont start, you can recover with the Windows XP CD. You start from the CDROM, and you get to a screen where you press ‘R’. You then get a screen which says: Microsoft Windows XP recovery Console. The recovery console provides system repair and recovery functionality. Type EXIT to quit recovery console and restart the computer (not helpful!)
1. C:\Windows
Which Windows installation would you like to log onto? (number 1 of course but if you press 1 it goes to the c:\windows prompt, and you can only press one key.) How do you repair the system?
The error message on startup is that a file is missing: c:\windows\system32\config\system, and the system halts.