HTC Desire HD Firmware Downgrade Guide
When HTC released their 1.72.405.3 OTA update for the HTC Desire HD, it could not be rooted and many people got stuck with the stock ROM. Now, thanks to XDA member CuBz90 we have a downgrade method. After this process, you can use any root (+ S-OFF) method you want, your device will be just like any other Desire HD with older build version. Downgrading will completely reset your device to factory defaults, so remember to back up.
The whole process is delicate, so be sure to know what you are doing before proceeding.
Originally posted by CuBz90
Here is a guide to downgrade from 2.37 [100% Confirmed]
Special thanks to har0ld for guiding me through this
1. Create a Goldcard (I strongly recommend using the Goldcard Helper from the Android Market)
2. Download this ROM – Mirror
3. Put the PD98IMG.zip onto the root of your SDCard
4. Boot phone into Bootloader (hold volume down whilst power on), follow the steps and continue to update