Well there's your problem. When you just delete folders all willy nilly, it leaves behind many registry entries that can cause many problems with your system such as the ones you're having now.
Here's something that may help you, CCleaner
. It will clean your system of any "unused and old entries, including File Extensions, ActiveX Controls, ClassIDs, ProgIDs, Uninstallers, Shared DLLs, Fonts, Help Files, Application Paths, Icons, Invalid Shortcuts and more..."
Download it and give it a run. It's free and very easy to use.