Last wednesday the Android 2.2 was announced. I read in many websites that it is faster and it has some new functionalities, like thetering and to be a Wifi-hotspot.
So How to install it? To know each one to download, access "Settings" - "About the phone" in the end you will see your Build Number. If you is ERE27 you should download this file:
PS: Sometimes they change the end from 1e519a24 to something else, maybe it is some small changes. So if the link is broken, please let me know.
1. Rename the file to update.zip and copy it to your microSd
2. With your nexus one off press trackball and press the power button
3. You will see a white screen with 3 Androids in Skates.
- Volume down, move menu down
- Volume up, move menu up
- Power button is Enter
- Select "Bootloader"
4. Next screen select "Recovery"
5. Your nexus one will reboot and it will show you a Android screen with a exclamation inside a triangle
6. Press the power button and volume up at the same time.
7. Now using the trackball select "Apply sdcard:update.zip" and let it execute
Tested and running. Android Version 2.2. Your nexus one doesn't need to be rooted to use this process.