This guide applies to rooting your HTC Desire HD version 2.3.5 on either Linux or OS X, I haven’t tested on other versions so I can’t guarantee that the process will work for other phones or android releases.
Step 1. Download the Ace Hack Kit.
Download link: http://tau.shadowchild.nl/files/aahk-12062012.zip
Note – this particular kit was from June 2012, you can check the following thread for the latest download link: http://forum.xda-developers.com/showthread.php?t=952352
Step 2. Open up a Terminal
Step 3. cd to the hack kit download directory
Note: your file name for the hack kit may be different if you have downloaded a newer version than me
Step 4. Plug in your HTC to your USB port with the USB lead provided
Step 5. Make sure that your phone is set to Charge Only. Do this by pulling down the top bar and checking that it says Charge Only. If not, select to change USB connection type and select Charge Only.
Step 6. Make sure your phone is in USB Debugging mode. This is important or the hack kit will fail to detect your phone when it’s plugged in. To make sure this is on, go to Settings -> Applications -> Developer -> USB Debug turn on
and run the script
Step 8. You will be presented with a menu of options. Press 1 to run Hack Ace.
Step 9. Follow the on screen instructions. In some cases, the script will inform you that it needs to downgrade the current ROM in order to exploit it. It will ask you if you would like to download the older ROM and process. Press Y to all. Once the ROM has downloaded, your phone will reboot. Press Volume Up and Power when the red symbol appears.
Your phone will reboot 1-2 times, repeat the procedure of Volume Up and Power.
A white screen will appear and start going down a check list of items. Don’t press anything, just let it do it’s thing.
Finally when it completes it will ask you to Press Power (to reboot). Don’t power off unless it tells you otherwise.
When it reboots again it should have the new older ROM on and boot into your regular phone ready for set up. Click through the menu’s and then turn on USB debugging like above, and make sure it’s set to charge only. Then run the hack-ace.sh script again and repeat the procedure on the older exploitable ROM.
Step 10. After hack-ace.sh has run and you have followed the instructions, your phone will reboot. Congratulations, you have rooted your phone. Feel free to put any sim card in, or to customise it how you please