This is how I've done it after reading dragon24's tutorial:
1 - Download the files on the first post, testmode 2.3
2 - In an 2GB SD card put WINCEIMG.BIN & WINCEIMG.CKS that are on the MyFlash folder on the root, create an testmode dir (with test mode in it).
3 - Start your car
4 - Press and hold the menu, map, eject buttons at the same time and hit the reset button.
5 - Once you hit the reset button, you will hear a pop sound from your speakers.
6 - Then the DVD/CD drive will load. When you hear this let go of the eject button but continue to hold menu and map buttons.
7 - This