Oh my, the pain I cause myself by 'tweaking' my Windows installations. After all these years I should know better than making low level changes to things I don't fully understand.

What did I do this time? Well, one of the computers I use was suffering from an overzealous Group Policy, which I have no control over, and locks down some useful windows features such as the ability to disable the crappy screen saver. Whenever I manually hack the registry to change these settings they are reset after a couple of minutes by the Group Policy updater.

Grrr, what could I do, this screensaver is wasting at least 2 minutes of every day so let's do something that will take about 4 hours to recover from. YEAH! That is it, I'll revoke the System account's write rights and ownership on these registry keys so it cannot change them. HAHA, I win..... yep it worked until I rebooted... bloody Blue Screen Of Death with a very undescriptive error that no one else seems to suffer from according to Google.

I quickly, as in subsecond, realised this BSOD was due to my faffing around with low level registry privileges. Now, how am I going to fix this considering I cannot boot into Windows (not even 'safe mode' or 'last known good mode' worked).

A quick Google pointed me to a Microsoft Knowledge Base article which describes how to restore a corrupt registry. Great, if it wasn't for the fact that it relies on a recent system backup (which I am too clever for to waste my time on) or Windows' System restore (which I cleverly disable to save disk space and banging around on the hard disk).

So, it looks like I need to do this the hard way and figure out how to load the registry and change the privileges back. Fortunately the disk with the corrupt registry is a virtual hard disk so I mounted it as a second disk in another (Working) VMWare image. If the disk had not been virtual I would have had to take it out and attach it to another system.

Once booted into the working VMWare image I found out that it is possible to load any registry hive from a file (<disk>\windows\system32\config) into the standard Windows Registry editor by selecting HKLM and then clicking Load Hive. The way this works is not very intuitive, click here for details.

Once the corrupt registry was loaded, I reverted back the changes, unloaded the hive, kept my fingers crossed and rebooted....... and it bloody worked, woohoooo.