I used a piano wire. Make a hole through the seal then feed the piano wire with wooden pegs wrap the wire on each side. With two people like sawing wood you'll saw (cut) the seal all the way around and the window and it will be removed without breaking. DO NOT FORCE THE WINDOW OUT IT"LL BREAK!!!!! George
If you plan on doing more than one window, get yourself a cold knife. Available at most auto stores. Costs about $8-10. Works great and it is a one person job.
Here is one from Amazon: http://www.amazon.com/exec/obidos/t.../ref=sr_1_5/104-1627436-2366305?v=glance&s=hi
What I do is use a regular utility knife to cut around the perimeter of the glass to remove excess windshield sealer. Start the cold knife in the corner by placing the blade parallel to the glass edge and rotating the blade under the glass. Keep the blade below the glass surface and parallel to the surface. Will work easily with a constant slow pull. Good Luck!