Hey, could anyone tell me if there's a simple way of doing, say - UNinstalling Windows Installer, then reinstalling it, and taking me step-by-step?

I tried following Microsoft's advice, but it didn't do a SINGLE thing to help, I think it only made it worse.

And Windows 7/64-bit.

Have you checked your machine, very well, for malware? That is probably the most common reason for installer not working.

If you are sure your machine is clean, have you tried repairing your OS? You need the installer to install and uninstall anything that uses the MS installer.