I am assuming you know how to use ADB and Fastboot as well as some basic OS knowledge be it DOS, OSX, or Linux.
This will do the followings to your Nexus One:
1. Reset your system files to the original system files.
2. Reset your kernel/boot image to the original shipping boot image.
3. Reset your recovery to original recovery (if you wish).
This will not relock your Nexus One. Once you unlock your phone, you are stuck for now.
This is for those of you who decided to flash a few different ROMs and want to restart from scratch.
You may get the Original Shipping Image from HERE or thru Modaco HERE. [22607 build]
MD5sum for the images is: bef86698cafc88ca03fff5758571d9d6 (per DroidDrop)
As before, if you mess up your phone or your computer, you are on your own. I take no responsibility on what you do with your phone or your computer.
Brendenk posted a nandroid back of his fresh image here If you don't want to do an actual factory restore, try this first. If you really really want to do it your way then...
Step 1. Disable backup my settings under privacy settings.
Step 2. unzip the original shipping ROM and put it somewhere you can find.
Step 3. Plug in Nexus One with USB to computer (enable usb and debug modes)
Step 4. adb reboot bootloader (which will boot into the bootloader)
Step 5. Confirm fastboot connection fastboot devices
Step 6*. fastboot erase userdata
Step 7*. fastboot erase cache
*If step 6 and 7 does not work, and if you have Amon_RA's recovery installed, you can do a factory data wipe from there.
Alternately, you can also do a factory data wipe within Android. Settings => Privacy Settings => Factory Data Reset.
Thanks to Brian and setzer715.
Step 8. Go to the directory that you stored your unzipped files.
Step 9. fastboot flash userdata userdata.img
Step 10. fastboot flash boot boot.img
Step 11. fastboot flash system system.img
Step 12. Skip to step 13 if you want to keep recovery (assuming you have a modified recovery such as Amon_RA's recovery). If not fastboot flash recovery recovery.img
Step 13. fastboot reboot
Step 14. After the system boots up and while setting up skip setting up with the google account and you can setup accounts later. This will prevent the phone from pulling down the previous settings (downloaded apps, wallpaper etc) from google.
Step 15. You are done. Enjoy.
Source: Modaco for the ROM Image and HTC for the Instructions.
This post can and will be updated without notice. Keep checking here for the up to date details.
The following information came from user tuffCookie (for those with unlocked bootloader):
ok, after researching, i finally figured it out.
If you have a rooted N1 with a LOCKED bootloader and want to bring it back to complete stock, follow my steps below.
DISCLAIMER: I am not responsible for any damages you may cause to your phone. Proceed at your own risk!
BEFORE YOU BEGIN: Just to be safe, make sure your battery is fully charged.
1) Find and download FRG33 IMAGE FORMAT from MoDaCo here: http://android.modaco.com/content/go...root-insecure/
2) Rename the file to PASSIMG.zip
3) Place the zip file on the root of your sdcard
4) Reboot into bootloader (power on your phone while pressing the vol down button)
5) Bootloader will automatically find and check PASSIMG.zip. Give it a minute and it should eventually show "Parsing....[SD ZIP]" and a list showing boot, bootloader, radio, recovery, etc and ask if you want to start the update. Press vol up for yes.
7) The update process will begin and automatically start flashing each item on the list. DO NOT POWER DOWN THE DEVICE DURING THIS PROCESS!!!
8) When it asks to reboot the device, press vol up for yes.
9) Now you're back to complete stock! If you want, you can go into settings and do an OTA system update.