Perhaps someone else will have more knowledge about this particular problem than me. However, it does sound like there's been a problem with your windows registry, for whatever reason. The registry holds links to current programs' uninstallers, allowing you to easily get rid of them. Since this has been screwed up, you can still go to the directories of the programs and uninstall them. Or, what I would do, just delete the directories, and then delete every occurrence to the program in the registry. That is what an uninstaller does anyway.