Windows 7 fix for crashing Windows Installer errors - cannot install or uninstall MSI packages

I ran into this error earlier today on my laptop and I figured I'd share the fix on here because it might happen to you after you have installed and/or uninstalled many programs on your Windows 7 computer. There is an ongoing discussion in the Technet forums here and a great blog entry with screenshots on how to fix it here.

Long story short, you need to delete the registry entries that may live under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SQMClient\Windows\DisabledSessions.
Hopefully, this will prevent you from uninstalling and reinstalling in desperation to get things working!