I have a Droid 1. I used this method to go back to stock 2.01. (MY Droid has an electrical short in it and I do this about once a week - for only 1 more week)
http://www.droidforums.net/forum/hacking-help/37717-unroot-unbrick-using-sbf-post-ikithme.html
First make sure your Droid is fully charged before doing this. Data on the SD card is not affected.
1. on #3 When it says holding "up" on the DPAD depands on whether you are holding the phone horizontal or vertical. Since I was holding my Droid in the vertical direction, you hold "right" on the DPAD. If you hold your Droid horizontally, the you press the DPAD in the up position.
If you hold the DPAD down correctly, you will get basicaaly a blank screen with the words BOOTSTRAP (and other words) on it.
My DPAD is very sensitive so I use a ballpoint pen to ensure I am holding it correctly.
After you are back to 2.01, I recommend that you plug your Droid into the AC Adapter until the updates are applied.
Once I was back to 2.01, I just accepted all the updates over the air. This took about an hour. Remember you must manually accept each of the updates.
Once all the updates were applied, I updated all stock apps. Finally, I re-added my apps from the App Market or Amazon.
I found that the App Market does NOT remember 100% of all the free apps that you downloaded (for me all purchased apps were remembered), so I picked up as many of the free apps from Amazon, then the remainder from the APP Market.
Good Luck,
Bob