A. I include this as I had the exact problem on site a couple of days ago and I want Administrators to be aware that this can be done.
If the scheduler service is running on your PC (or if you can start it) you can submit the registry editor to start via the scheduler and it will then be started under the system context. For example
C:\> <b>at <1 minute in the future> /interactive regedt32.exe</b>
One minute from submission regedt32.exe will be started giving you full access to the registry. Cool!
You can also re-enable the tools by writing a small .reg file and double click on it which gives full access:
Save as disableregistrytools.reg, double click from Explorer and you will have full registry access.