Insert the Windows XP installation CD
Then restart your system
Then Press the "R" key at the welcome screen this will let you enter the setup
Enter admin password on promoting you to do so
you will see that the recovery console will launch
then type the commands that I mention next and press enter after each command
md tmp
copy c:\windows\system32\config\system c:\windows\tmp\system.bak
copy c:\windows\system32\config\software c:\windows\tmp\software.bak
copy c:\windows\system32\config\sam c:\windows\tmp\sam.bak
copy c:\windows\system32\config\security c:\windows\tmp\security.bak
copy c:\windows\system32\config\default c:\windows\tmp\default.bak
delete c:\windows\system32\config\system
delete c:\windows\system32\config\software
delete c:\windows\system32\config\sam
delete c:\windows\system32\config\security
delete c:\windows\system32\config\default
copy c:\windows\repair\system c:\windows\system32\config\system
copy c:\windows\repair\software c:\windows\system32\config\software
copy c:\windows\repair\sam c:\windows\system32\config\sam
copy c:\windows\repair\security c:\windows\system32\config\security
copy c:\windows\repair\default c:\windows\system32\config\default
now you need to exit from the recovery console and restart the computer you will see that the problem is solved see if this helps, if due to corruption you have lost any of the data you can use the data recovery by stellar which will help you to make the system fine as it was before Christmas