Windows Installer Problems

[Sailor Steve]

This all started with a problem with Adobe Reader. It keeps saying there's an update, but it won't let it happen. It says there's a problem with Windows installer. I didn't really care, so I just ignored it.

A second problem was with AVG antivirus. One day it just quit working, and when I tried to redownload and reinstall it nothing happened. So I found Microsoft Security Essentials and things have been fine.

Today MSE suddenly said it wasn't working any more and I needed to upgrade. Upgrade doesn't work. So I try to reinstall it, and it says there's a problem with Windows Installer. I tried a couple of different programs that claimed they could fix it, with no luck.

So I tried to update Windows Installer, and it didn't work. So I found there's a newer version and downloaded it. When I tried to run the newest version of Windows Installer, it said I couldn't because there was a problem with - Windows Installer.

So how do I fix this thing anyway?