How to recover from a corrupted registry

How to recover from a corrupted registry that prevents Windows XP from starting.Registry is damaged or corrupt which prevents Windows to boot to desktop. you find a error massage

Windows XP could not start because the following file is missing or corrupt: \WINDOWS\SYSTEM32\CONFIG\SYSTEM

This post describes how to recover a Windows XP system that does not start because of corruption in the registry. This procedure does not guarantee full recovery of the system to a previous state; however, you should be able to recover data when you use this procedure.

Warning Do not use the procedure that is described in this post if your computer has an OEM-installed operating system. The system hive on OEM installations creates passwords and user accounts that did not exist previously. If you use the procedure that is described in this post, you may not be able to log back into the recovery console to restore the original registry hives.

Note Make sure to replace all five of the registry hives. If you only replace a single hive or two, this can cause potential issues because software and hardware may have settings in multiple locations in the registry.

Follow the steps for system which were installed by Windows xp disk.
1.Start the Recovery Console.
2. At the Recovery Console command prompt, type the following lines, pressing ENTER after you type each line:

cd system32\config
ren system system.old
ren software software.old
ren SAM SAM.old
ren security security.old
ren default default.old
cd \
cd windows\repair
copy system C:\windows\system32\config\system
copy software C:\windows\system32\config\software
copy sam C:\windows\system32\config\sam
copy security C:\windows\system32\config\security
copy default C:\windows\system32\config\default

Note The repair directory contains a copy of the registry from the first time the system successfully booted after Windows was installed, or from the last time that the customer performed a full system state backup. Any changes that the customer made to the computer since the repair copy of the registry was created are lost. Also note that this procedure resets your password to the password that was used when you first installed Windows XP or that was used the last time that you backed up System State. If the customer cannot remember this password, you may have to use a more current backup of the registry from the System Restore folder (%systemdrive%\System Volume Information\_restore xxxxx \RP xx\snapshot) instead of from the Repair folder.