When a program does not uninstall correctly and it remains as an option in the 'add or remove programs' control panel. This can happen due to poor coding or an error in the un-installation process.

in the registry, navigate to:

'HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall'
Look for the offending program entries and delete them. Note that some programs may be listed with a string of letters and numbers. Open the value inside these keys to see the actual name of the program.