You could try the C25K program, if you want to run but want to start out pretty slowly. In the beginning, it only has you running for like 90sec or 2 minute intervals with walking inbetween... The elliptical is also a great option too, a little less impact and would maybe be a great alternative to running until you get a little more used to doing regular cardio exercise. Don't give up though, whatever you do. To lose weight, you have to challenge yourself and work hard, just don't get yourself burnt out before you even get going
I know there are links on this forum to the C25K program and podcast stuff. I have been doing it now for almost six weeks and am really enjoying it. It's getting the running back into my routine on a regular basis and I truly feel like it is really helping the fat come off.
-Sam