I recently bought an HD2, which originally runs Win6.5. But currently has a very modern version of Android installed.
Is it necessary to re-install the original OS in order to unlock the phone?
I recently bought an HD2, which originally runs Win6.5. But currently has a very modern version of Android installed.
Is it necessary to re-install the original OS in order to unlock the phone?
90% chance - no, 10% chance - yes.
The Android operating system is designed specifically for each device, which is why different phones get platform updates at different times. You're at an advantage starting with an HTC phone, as they build several Android phones.
Your best bet is to find an unlock process for an HTC phone as physically similar to yours as possible (physical in terms of hardware; processor, memory, etc.). If this does not work, chances that you will get anything to work is slim.
In order for the HTC HD2 to run Android, the device needs to have a custom bootloader running Hardspl and radio version, which means your device IS ALREADY unlocked.
As for the device been rooted, 99% of the Android versions on the HD2 are rooted.