We all install many programs on windows by time and some times when you try to uninstall a program it does get uninstalled so it leave registry in a mess and the files of the programs are left undeleted, due to the same reason you may find problems in removing the anti spyware or anti virus programs. Improper Uninstall of programs can cause invalid entries in add/remove programs.
AppRemover is a FREE utility which comes to rescue in this kind of situation which lets you remove various anti spyware and anti virus programs when you face problem in uninstalling them.
AppRemover small .exe which does not require any installation, so you just need to run the executable to run AppRemover.