What:

HTC comes stock with 2.x firmware which cannot be rooted. Think of it from an iOS perspective, you’re on 4.x which can’t be jailbroken, we need to get down to iOS 3.x so to speak. So once we downgrade to a rootable firmware, we can root or jailbreak and install ClockworkMod, or Cydia as the iOS equivalent.

About:
The problems started when HTC released their 1.72.405.3 OTA update. That update could not be rooted, and many people got stuck in stock roms. Now a downgrade method has arrived! After this process, you can use any root (+ S-OFF) method you want. Basically your device will be just like any other Desire HD with older build version. Downgrading will completely reset your device to factory defaults.

System requirements:

  • HTC Sync (or ADB drivers)
  • Desire HD with build number 1.72 or higher (2.37 cannot be downgraded yet, just wait..)

How to downgrade:

Section 1

  • Disable any antivirus software
  • IF you have a branded / regional (like US) device, you have to make a Goldcard. Use “mmc2″ instead of “mmc1″!!
  • Download the attached file and extract it
  • Get stock 1.32 PD98IMG.zip ROM, mirror
  • Put the PD98IMG.zip into your SD card. Do not put it into a folder, and do not extract it.

Section 2a [For Froyo ROMs, 1.7x and 1.8x]

  • Connect Desire HD to a computer. Charge only, USB Debugging enabled!
  • Open up a cmd and go to Downgrade folder, execute commands:
Code:
adb push psneuter /data/local/tmp
adb push misc_version /data/local/tmp
adb shell chmod 777 /data/local/tmp/psneuter
adb shell chmod 777 /data/local/tmp/misc_version
adb shell /data/local/tmp/psneuter
adb shell

Section 2b [For Gingerbread ROMs, 2.x]

  • Connect Desire HD to a computer. Charge only, USB Debugging enabled!
  • Open up a cmd and go to Downgrade folder, execute commands:
Code:
adb push misc_version /data/local/tmp
adb push GingerBreak /data/local/tmp
adb shell chmod 777 /data/local/tmp/misc_version
adb shell chmod 777 /data/local/tmp/GingerBreak
adb shell
./data/local/tmp/GingerBreak

Section 3

If you got “#” in the result, you have temporary root! Proceed with commands:

Code:
cd /data/local/tmp
./misc_version -s 1.31.405.6
  • Close the CMD. Reboot while holding volume down, it will go to the bootloader
  • Follow the instructions (start the update)

Done!

[via XDA]