[Ubuntu] Reverting upgrade from thir party PPA

History
I got new hardware for my PC at work (i3-2100 with integrated Intel HD Graphics 2000). My Ubuntu 10.10 installed didn't feature proper drivers for this GPU, but some folks over the Web advised to add xorg-edgers PPA which hosts bleeding edge version of Xorg and drivers.
It's worth saying that I my Xorg rejected to extend my desktop to both monitors after this upgrade :)

Task
So I started searching for the way to revert this update :)

Solution
Finally Synaptic saved me! I'll appreciate if somebody will teach me how to do the same from command line.

So:

1. open Synaptic
2. select group by Origin (bottom left corner)
3. in the list on the left find the source repo you did the upgrade from
4. now select installed packages (from this repo) one by one and for each to Package - Force Version... (Ctrl + E)

After that you could remove the PPA and don't do that again :)
Some more helpful info is available at https://help.ubuntu.com/community/CleanUpgrade