After spending a bunch of time figuring this out through many incomplete guides, I thought I would post one here. These are very direct instructions. If you don’t understand them, please don’t proceed. Do a little research and come back. As always, I am not responsible for you bricking your phone. This WILL void your N1 software warranty. You have been warned.

If you are on T-Mobile, there are much easier directions for you out on the web. These directions are ONLY for those on AT&T running a Nexus One made for AT&T.

Here goes:

1. Download the SDK

2. Install the SDK

3. Add the USB driver package to the SDK and install/update it http://developer.android.com/sdk/win-usb.html

4. Connnect your phone, enable USB debugging (Settings>Applications>Development) and run adb devices from your tools dir under the SDK dir. This should show the serial number for your device. If it does not, troubleshoot the previous steps until it does.

5. DL the following packages:

a. ERD79: http://coblitz.codeen.org/www.romraid.com/paul/nexusone/22607-ERD79-update-nexusone-stock-images.zip

b. ERE27 Update: https://android.clients.google.com/updates/passion/signed-passion-ERE27-from-ERD79.a487b405.zip

c. FRF50: http://rapidshare.com/files/390455084/signed-passion-FRF50-from-ERE27.1e519a24.zip

d. FRF72: https://android.clients.google.com/packages/passion/signed-passion-FRF72-from-FRF50.bc033f9e.zip

6. At a command prompt under the SDK\tools directory, issue the command adb reboot bootloader. Your phone will boot into the bootloader.

7. At the same prompt, unlock the phone by issuing the command fastboot oem unlock. Read here for details http://www.ihackintosh.com/2010/01/how-to-unlock-the-bootloader-on-nexus-one-to-run-custom-os/

8. Reboot

9. Extract boot.img, system.img, and userdata.img from the ERD79 zip to the tools dir

10. Once your phone is booted, issue the command: adb reboot bootloader. Your phone will boot into the bootloader.

11. Issue the following commands:

a. Fastboot flash userdata userdata.img

b. Fastboot flash boot boot.img

c. Fastboot flash system system.img

d. Fastboot reboot

12. Once booted, mount the SD card as a disk in Windows. Copy ERE27 to the SD card and rename it to update.zip. If you have visible file extensions turned off in Windows, just rename it to ‘update’.

13. Eject the USB drive in Windows.

14. Power the phone off. Then, power it back on while holding the trackball down to boot into the bootloader.

15. From the bootloader, press the power button to boot into the bootloader

16. Use the volume down button to get to the recovery menu item, then use the power button to select.

17. When you see the exclamation point, press power and volume up at the same time.

18. Using the trackball, select “apply SD card update”

19. Wait until the update is complete. DO NOT, under any circumstances, pull the battery or fuck around. One of the updates is a radio update, and if you fuck it up you will brick your phone. The update will boot into several odd modes but will eventually (~10 minutes later) boot up normally.

20. Once booted, repeat steps 12-19 with the FRF50 update

21. Once completed, repeat steps 12-19 with the FRF72 update

22. Done