How to update your Nexus One to Froyo
If you are running stock recovery (not rooted phone):
- Download the Android 2.2 firmware for the Nexus One
- Rename the file update.zip and copy it to your microSD card via USB. [Note: make sure the file is named update.zip and not update.zip.zip.]
- Power down your phonez
- Hold down the “Volume Down” button and power the phone on.
- A screen should appear showing your phone’s system searching for various files. Scroll down to “recovery” and press the “Power” button.
- When you see the triangle with an exclamation point symbol, press the “Power” and “Volume Up” buttons at the same time.
- From the menu that appears, select “Apply sdcard:update.zip.”
- When the screen displays “Install from sdcard complete” select “reboot system now” and wait for the phone to power back up. It may reboot itself instead of asking you to do it.
To restore the root, you can use Quick rooter for stock FroYo systems by Cyanogen.
If you have a rooted phone:
- Flash FRF50 (Froyo) pre-rooted update zip by Paul from MoDaCo.