RenderMonkey Installer Error

This problem probably has nothing to do with RenderMonkey; it's just Windows XP Registry horror.

I am attempting to install ATI RenderMonkey 1.62, and it manages to get everything right until just about the end of the process (maybe even the last step; progress bar says 0 seconds remaining, label above it says "Registering extension servers...") where it gives me the following error and gives up:
Looking in regedit, it seems that the key already exists, though that shouldn't hurt anything...

This fails with every user account, and I do not feel like reinstalling Windows.
Have you seen this before?

I've seen minor registry corruptions where windows had the incorrect permissions applied to certain subbranches, locking even administrator out.

In some cases doing a system restore to an earlier date fixed the problem, but in one case I had to run some kind of microsoft repair tool that I found on their website to re-apply all registry branch permissions so administrator could modify them again and install software.

(Administrator does not have full access to all system resources - it can be locked out of certain things as well. Only system has full access.