-Problem-
Windows could not start because the following file is missing or corrupt:
C:\windows\system32\config\system


-Fix-
1. Reboot the computer and before the Windows Logo screen appears tap F8.
Select the option to boot to recovery console. If you don't have the option
to boot recovery console use your XP/2000 CD and boot from it. Once it loads
select the "r" option to repair by recovery console.

2. Select the windows install to use. Most users will select "1" unless you
are running a multiboot system. Enter the administrator password. If you
forgot your administrator password see this site on password retrieval.

3. At the console type: chkdsk /p
Once it finishes restart the computer. If its not fixed do #4.

4. This will only work if you had system restore turned on (by default it's turned on).
At the console: C:\Windows>CD C:\system~1\_resto~1
C:\system~1\_resto~1\>dir
After the "dir" command you should get a listing of folders like rp1, rp2, rp3,
etc, etc. Find the second highest number in the list. In this example I'll assume
rp46 is the second highest number.

At the console: C:\system~1\_resto~1>cd rp23
C:\system~1\_resto~1\rp23>cd snapshot
C:\system~1\_resto~1\rp23\snapshot>copy _registry_machine_system c:\windows\system32\config\system
Overwrite system [y,n]: y
1 file copied
C:\system~1\_resto~1\rp23\snapshot>exit