Have you tried a clean reset?
1) Press and hold the Calendar button, the Power button, and the Messaging button.
2) While holding these buttons, use the stylus to lightly press the Reset button on the bottom of the HP iPAQ.
3) When the Pocket PC screen begins to fade, release all of the buttons, and then remove the stylus from the Reset button.
The HP iPAQ restarts and powers on
Given everything you've tried, and assuming a clean reset does not resolve the issue, I think this is a hardware issue that likely needs to be repaired through a repair shop. Pocket PC Techs is highly regarded by many on this and other pocket pc forums:
Pocket PC Techs
To stop the pocket pc from trying to turn on bluetooth every time you soft reset the device, you may need to remove a shortcut from the Startup folder. Look here:
\windows\startup
julie