If you are on a modded Nexus One, with either a root on the stock Android 2.1, or with the HTC Desire ROM and are too lazy to return to stock to receive the OTA update, this method is for you. As a pre-requisite, you will need to have an unlocked bootloader, and root access on your Nexus One. You will also need to have the patched recovery-RA-nexus-v1.5.3.img recovery on your N1.