Los pasos a seguir son:

1. Power on your Desire then connect to your Charger and Fully charge until the LED changes Green.
2. Disconnect your phone from the charger and then power off.
3. Reconnect your phone to your charger with the power off and wait for the green LED.
4. Disconnect the phone from the charger and power it on.
5. Once the phone has fully booted / ready to use … power off again.
6. With the power off connect the phone to the charger and wait for the green LED.
7. Disconnect from the Charger then power on and use normally.

Fuente:

http://www.htcdesireforum.com/htc-desire-how-to/calibrate-desire-battery-it-worked-for-me-!!/?PHPSESSID=384c4e341dbf3afb9dd2f8c8dcb30b33