In order to uninstall, it depends on which version of Windows you have:

For Windows XP:
To uninstall an add-in, go to Start...Control Panel...Add/Remove Programs.  Look for the add-in (it starts with "Sperry Software - name of add-in") and select "Remove".

For Vista and Windows 7:
To uninstall an add-in, go to Start...Control Panel...Programs and Features.  Look for the add-in (it starts with "Sperry Software - name of add-in") and select "Uninstall".