Cannot uninstall any programs

Here's a strange one. I'm not sure why this happened, but I want to post the issue here for anybody else who might run into it and maybe someone might have seen it and knows what might be happening.

This problem occured on Windows XP.

While cleaning up all the junk software on a machine we uninstalled MSN Toolbar. After rebooting we found that when opening add/remove programs all the programs lost their change/remove buttons. Nothing could be uninstalled.

I took a closer look and found that the HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall registry key was empty. Something appears to have deleted it.

I started digging through restore points and found that the problem occured after uninstalling the MSN toolbar. The MSN toolbar removal uninstalled a program called "Microsoft Default Manager." The removal of the MSN toolbar created 3 restore points, one for each program it removed including the Microsoft Default Manager which was the last program to be removed.

I was able to successfully perform a system restore to undo the removal of the "MIcrosoft Default Manager" and then my registry was back to normal and the remaining programs could be uninstalled again.

A very strange issue that I think I have seen before, but have never narrowed it down to what it was. Now, I know that this very simple uninstallation of MSN toolbar really screwed things up.

It would be interesting to see if the problem can be duplicated at will on other machines. It seems if that were a common problem, it would have been fixed by now, or at least widely publicized.

This is a bit of an older machine with a lot of other junk on it. So its hard to say what actually causes the problem to happen. The MSN toolbar itself was probably an older installation.