I use Fastboot Commander which as a GUI based tool is the easiest way I have found to flash the HBOOT on your HTC Desire.
A little disclaimer: Fastboot Commander is a tool that should only be used if you are comfortable messing about with your phone. This has the potential to brick your phone or to put it simply, break it!
However, if like me you like to tinker with your phone, Fastboot Commander will allow you to upgrade your ROM, your radio and your HBOOT without much fuss.
What is fastboot?
“Fastboot is a command line tool used to directly flash the filesystem in Android devices from a host via USB. It allows flashing of unsigned partition images. It is disabled in production devices since USB support has been disabled in the bootloader. You must have an Engineering SPL, or an SPL that is S-OFF.” Find out more from the Cyanogenmod Wiki.
Fastboot Commander is a tool that harnesses the power of fastboot and puts it into a package that the average person can use.
Simply download it from the link above and run it on eiher, Mac, Windows or Linux. There is no installation – it just runs as a JAR programme.
Step 1: Put your HTC Desire into fastboot mode by powering the device off. Wait a few seconds, then hold the volume down button and press the power button. After a few seconds your phone will boot into a screen that gives you several options, including fastboot and recovery. Select the fastboot option.
Step 2: Do nothing!
Step 3: Go back to your computer and run Fastboot Commander.
Step 4: Connect your phone via USB.
Step 5: Now all you need to do is select the action you wish to complete e.g. in the picture shown I was updating the radio. I selected the radio button and selected the appropriate file and then selected open. After a minute or so my HTC Desire had a new radio image installed. Updating the radio has the advantage of bringing several improvements to mobile reception, data transfer, battery life and better GPS.
If you are thinking about installing a custom rom on your HTC Desire you will need to update the default radio as many roms require you to update to a newer radio. I recommend that you use Fastboot Commander to do this.
Let me know if you have a better method or if you found this tool useful in the comments below.