How to Recover From a Severe Windows Registry Error

The Windows Registry is basically a small database that keeps track
of customized settings and preferences under different keys, or hives.
It is hierarchical in nature and stores data under various headings
such as local machine, current user, and current configuration. Any
change to the appearance of your desktop, changes in program
preferences, and the addition or deletion of software will add,
modify, or delete various registry keys. Over time, the registry
becomes quite fragmented and a bit disjointed. If an important system
file in the registry becomes corrupt your computer may become unstable
and experience blue screens, boot errors, or software errors. The
severity of your issue will determine the troubleshooting steps to
take.If your computer won't boot due to stop errors (blue screens) and
is giving you a message such as, "Windows could not start because the
following file is missing or corrupt:
\WINDOWS\SYSTEM32\CONFIG\SYSTEM", you obviously have a critical error
to deal with. At this point you will need a Windows operating system
disc inserted into your CD drive. Boot off of that disk and press R
when offered a choice of what you wish to do. This lets the operating
system know you do not want to reinstall Windows, but rather just
attempt to repair it. At this time, you have the choice to press R for
an automatic repair attempt or C to enter the Recovery Console. Choose
C for the Recovery Console. Otherwise, Windows attempts to basically
reinstall itself which will wipe out most of your settings and
programs.Select the Windows installation you want to enter. There is
probably only one listed so press 1. Enter the Admin password, if you
supplied one during installation. At this point, you are in the
Recovery Console and are probably looking at a prompt something like
c:\Windows\. What you need to do is copy and replace all of your
system registry files from c:\Windows\repair to
c:\Windows\system32\config. Specifically, the files you are copying
are default, SAM, Software, Security, and system. These make up the
major registry keys.After this is complete, exit the Recovery Console
and your computer will reboot. You may have to wait several minutes as
your operating system boots with a different set of registry keys from
the last time. Optionally, before going to such extreme measures as
the Recovery Console, you can press the F8 key a couple of times as
the computer boots up and you will be provided with several different
boot options. Select Last Known Good Configuration and see if your PC
will be able to load the registry keys automatically. In practice this
never seems to work but it's worth a shot.