BleepingComputer.com: Windows Installer will not ininstall Itunes

When trying to uninstall itunes, I get a message that says: "the windows installer service could not be accessed". In checking in device manager I discovered that windows installer was running and checking the registry, windows installer is set to start automatically. I have also tried to change the registry setting to manual with no success. I have also tried to uninstall in the safe mode with no success. I have had trouble installing some, but not all, other programs. I am running Vista 64. Thanks in advance for your help.