For Windows 7 & Windows Vista: GMAP maps are stored at "%PROGRAMDATA%\Garmin\Maps" if they are installed as Administrator or at "%APPDATA%\Garmin\Maps" if they are installed without Administrator rights as a single user. You also have GMA and UCX files at "%APPDATA%\Garmin\Maps" since they are always installed for a single user.
Garmin maps with multiple IMG map tiles are normally stored in "%SystemDrive%\Garmin". They will also need keys in Windows registry for the path to several specific map files.
Older Garmin maps was not locked since the range of handheld units at that time didn't support any locked maps. Some map series continue to support those devices and still use the original not locked Garmin format.