Ok, here are some information to help other upgrading their locked GPS.
Everything in the first post is written for user how like to upgrade the GPS with the same firmware as they already has.
But wait, what if there is a new firmware for your GPS, do you then need to follow the steps in post #1. No.
Here is what I did on my Nuvi 2699 to upgrade it for second time with a patched firmware.
Wait until Garmin releases a new firmware for your GPS.
Take care if you upgrade your map and there is a new firmware, it will upgrade the firmware at the same time without asking.
But you can use the same steps if you upgrade the maps as well.
1. Make sure there is a new firmware for your GPS.
2. Connect it to your PC and start Garmin Express.
3. Update your GPS, but do NOT remove it from your PC or reboot it.
4. Copy the gupdate.gcd from the .system folder to your PC.
5. Follow steps 1-5 in first post.
6. Rename gupdate_patched.gcd to gupdate.gcd
7. Copy gupdate.gcd to .system on your GPS
8. Reboot, and GPS will upgrade.
PS step 5 in post #1 is missing an important step.
It is not clear what Window it referering too.
It should be written:
5) Start patcher, drop the gupdate.gcd in its window. The patcher will provide the patched gcd file as 'gupdate_patched.gcd' in your chosen directory.