Big thanks to the folks over at this XDA thread that discovered the URL!

Disclaimer! We are not responsible for any harm that may occur due to your flashing or attempting to flash this rom

Here is the official download link from Google:

http://android.clients.google.com/packages/passion/signed-passion-FRF50-from-ERE27.1e519a24.zip

Google seems to have removed their link. I'm mirroring the file here. Man, you guys killed my Dropbox too! Here's another mirror. Let me know if the mirror stops working. I personally uploaded that file and verify its authenticity.
One our contributors confirmed a successful flash by using our instructions, so we have verified this now works. At this point, make sure you're running a completely stock Nexus One. NO WIPE was required to go from stock ERE27 to Froyo

What You'll Need To Flash This

  • At this point, Nexus One with the stock recovery and system image. Looking at the title, I'm guessing you'll need to be on ERE27
It's been rooted! See here and here.

How To Flash

I grabbed these instructions from Android Central, so be sure to show them some love:

  1. Download the update from here.
  2. Rename the file to update.zip. Note that if you're using Windows, just rename it to "update" (no quotes, of course) because it's already a zipped file.
  3. Copy the update.zip file onto your microSD card.
  4. With your Nexus One off, hold down the trackball and press the power button.
  5. You'll be booted into a white screen with three Android robots on skateboards. Select "Bootloader."
  6. On the next screen, select "Recovery."
  7. Your phone will reboot, giving you a picture of the Android robot and an exclamation point inside a triangle.
  8. Now press the power button and volume up button at the same time. It could take a couple of tries.
  9. Now (using the trackball this time) choose "Apply sdcard:update.zip" and let things run their course.

Ways To Root

The two biggest players in the Nexus One rom scene have already rooted the rom! You have two options:

I haven't tested either yet, but will as soon as I get home (in an hour or so).  Drop us a line if you've used either method.

What About AT&T Nexus Ones?

Users on unrooted AT&T Nexus One's will have trouble with the above steps since the rom is designed for coming from the ERE27 version of 2.1 which is T-Mobile specific. However, it seems that if your AT&T Nexus One has been rooted, you can flash the update using a third party recovery image and still have 3G. Here is a user report from XDA-Developers:

Installed Paul's Update using Amon_RA custom recovery on an AT&T. Confirmed that I have 3G coverage and everything seems to be in working order.
As of right now I can't confirm this - anyone with a rooted AT&T Nexus want to give this a try and let us know?

Anyone brave enough to try these steps? Be sure to drop us a line if this works for you.  I'll update this post as more information becomes available.