MF
Consider me an expert on this
I have done it once - actually Tuesday this week!
Go to Garmin.com
go to s/w downloads
download the GPS s/ware update applicable to your PilotIII (it is really easy and simply explained)
then go to Aviation database updates
download the database(s) that you want
A credit card transaction for 35usd plus VAT at 17.5% is then required to gain an unlocking key.
Plug the serial port connector into the back of your PC, plug the round female end into your Garmin. Put Garmin into sim mode
Go to wherever you've stashed the downloads, run the little exe files, key in the unlock code for the database and Robert is your mother's brother.
It really was simple, easily explained and pain free.
Stik