if the above download is not suitable - if you have a bootloader version 0.80.xxxx or below AND a current ROM of 1.21.xxx.x or below
r6-desire-root-alt.zip

If you have a bootloader version 0.75.xxxx or below AND a current ROM of 1.15.xxx.x or below
r6-desire-root.zip


The guide

Follow through these steps, one by one and at the end of it you'll have a rooted Desire with the latest ROM.

Note: This process will wipe your device and there is currently no option to backup your device ROM before you start.

    * Make your microSD card into a goldcard by following these instructions (it's a good idea to back up the contents of your card first!).
    * Unzip the file you downloaded to a directory, then open a command prompt / terminal window at that directory.
    * Copy the 'update.zip' file to your microSD. Do NOT rename it.
    * Turn off your HTC Desire, then turn it back on with the 'back' button held down. You'll see 'FASTBOOT' written on the screen in a red box. Connect the phone to the computer.
    * In the terminal window, enter either 'step1-windows.bat', './step1-mac.sh' or './step1-linux.sh' as appropriate.
    * Navigate to the 'BOOTLOADER' and then 'RECOVERY' option on the menu, using the volume buttons to move and the power button to select.
    * When a black screen appears with a red triangle, press and hold 'Volume Up' then tap 'Power'.
    * Your device should now be at the 'recovery' screen. Select the 'wipe data/factory reset' option, then select the option to 'Apply sdcard:update.zip'. This will take a little while, so go make a nice cup of tea. When the flash has finished, reboot, and you are DONE