search here ... search there ... eventually you will find what you want ... gotta try though :P
http://forum.xda-developers.com/showthread.php?t=472925
3. want to change GPS button action how?
open up a registry editor and go to
HKLocalMachine-Software-HTC-Biotouch-Actionscreen-APP_10
you will find a key named PATH edit it and input there tha path of your gps program i.e. \Strorage Card\Destinator\Destinator.exe
you must input and the .exe file with the path and becarefull for lower and upper casing letters.