This guide will take you through the steps of installing a custom ROM on your desire HD.
This method is used for most phones with a custom recovery.
DISCLAIMER- Follow this guide at your own risk i am not responsible for any damage you cause to your device.
1. First step is to pick a rom theres loads to choose from. Sense roms, Non Sense roms ECT. Best resource is here
2. For your first rom i would suggest using leedroid 2.2.2 download from here
3. When ROM has downloaded put the .zip on the root of your SD card (not in any folders).
4. Ok now Boot your phone into recovery. Open ROM manager app and select reeboot into recovery.
5. I will assume that you have already made a backup of your current ROM (how to flash custom recovery) If you havent do it.
Next you want to clear all the phones data to do this choose factory data reset option, then clear cache option then go to advanced and select clear dalvik cache option.
6. Ok time to flash your new rom in recovery choose INSTALL ZIP FROM SD CARD (Remember to navigate menu use volume up/down to move and power button to select.
7. Next you want to select the CHOOSE ZIP FROM SD CARD option.
8. Select the leedroid .zip from the menu and flash it.
DO NOT TOUCH YOUR PHONE NOW UNTIL IT REEBOOTS I CANNOT STRESS THIS ENOUGH.
It can take up to 10 mins for this to happen dont panic.
So your now running your new ROM happy days.
As with most roms the developer will suggest that you flash a recomended radio you dont have to but to get the full potential of your rom i.e Battery saving and speed its a great idea.
TO FLASH RECOMMENDED RADIOS READ HERE