Sorry, had to stop for dinner!
The reason you should start with the 10x not in the BT database is to force Garmin Mobile PC to use its Bluetooth option. If it discovers the 10x on a COM port instead of via Bluetooth, it will not get the ID and won't unlock the maps.
When Mobile PC starts (and after you choose the 'Use Garmin GPS' option),it will search for a Garmin GPS. You can confirm it has found one by clicking on the satellite picture in the top right corner. If you get a screen with the 10x identified and IDed, it should work fine. You won't get this if it finds the GPS using a COM port.
Once Mobile PC knows where to look (it saves the last used GPS port in the registry), you can add the 10x to the Bluetooth stack so other programs can use it.
Terry