You will need activsync (
Now let's start...
HTC Diamond (DIAM100)
The first make sure your device has Hard-SPL (
Step 03 and Done
Stock ROM (english, french, German, Italian)
Step 01 - activsync for synchronisation your mobile with PC
Step 02 - Hard-SPL Rom updater, or something crack you can say also
(here your HTC touch will prompt you give access, Click Yes, & restart and again start the process form step 01, once you started step 02 the phone will automatically turn off, or will be blacked out don't fear and do not remove the cable untill finish the process)
Step 03 - Choose the Language you want to be installed on your phone,
step 03 really begin to install to process, once its done automatically it'll restart the phone, WOW language has been change !!!!
Hope you Enjoy !!!!
I've tested by me 200% working Max 10min work,
Changed HTC Touche Diamond P3700 French to English, Awesome !!!!!!!