If Windows can no longer log on correctly or logs off again immediately after logging on, this is usually due to an error in the registry. This tutorial should only be used if no other access to the registry is possible.

First of all, you need a boot CD. UBCD4win is suitable for this. However, others can also be used. The only important thing at this point is that we get access to the file system.

Now go to the folder C:\Windows\system32\config and rename the following files:

1. SAM
2. SECURITY
3. software
4. default
5. system

These should now be backed up to another partition or similar.

Now go to the folder “C:\System Volume Information”. Here are several folders with data for the system restore. We look at the creation date and open one of the folders whose date is current. Here we find “RPxx” subfolders and open another one with a similar date. This again has a subfolder called Snapshot. This is exactly where we find the files we need:

1. _REGISTRY_USER_.DEFAULT
2. _REGISTRY_MACHINE_SECURITY
3. _REGISTRY_MACHINE_SOFTWARE
4. _REGISTRY_MACHINE_SYSTEM
5. _REGISTRY_MACHINE_SAM

We copy these to the folder C:\Windows\System32\Config and rename them back to their original names.

Now we restart. If the problem still persists, the process must be repeated with slightly older registry files.