Windows Installer Error

This solution didn't work for me. I did all the steps and replaced the
registry key, but nothing happened, i kept getting the same error.

I have the problem kinda pinpointed though: at least in my case, it's
caused by one of the windows updates - i haven't figured out which one
yet though. My next step will be install the updates one by one to
figure out which one is messing the whole thing up, but that takes a
lot of time :(

The weird thing is, with so many people complaining about it, howcome
haven't they issued a report about it yet... I'm seriously thinkin
bout going back to XP :(