I'm not entirely sure on the fully purpose of this, but it's possible to perform a FACTORY RESET when accessing the BootLoader / HBOOT screen.
A quick note:
FOLLOWING THESE INSTRUCTIONS IS ENTIRELY AT YOUR OWN RISK – these notes are purely for my own reference.
BootLoader / HBOOT
On my desire HD – to enter the BootLoader / HBOOT screen, perform the following steps.
- Remove the battery to reset the phone (you'll loose temporary data stored in the RAM)
- Re-insert the battery and PRESS AND HOLD the VOLUMN DOWN button and then also press the POWER button
- After a few seconds, a white screen with three ANDROID figures on the bottom of the screen will appear
In this BootLoader / HBOOT screen, you have several options – most of which I currently do not understand, but will update accordingly.
One of the options is FACTORY RESET.
To select this, use the UP and DOWN VOLUMN buttons to change the option, and press the POWER button to select the option.
During RECOVERY, and FACTORY RESET, pressing the VOLUMN UP + POWER button combination shows some debugging text / options – again, which I'm not entirely sure of.