Start with shorter workouts - aim for 20-30 minutes - but work out hard. If you get your heart rate up (buy a heart rate monitor) you will see results faster. Most people make the mistake of working out in their comfort zone and then get discouraged when they do not see any results (obviously do not push yourself too hard and get hurt). Add a bit of time (in 5 min chunks) till you can comfortably do 45 min - 1 hr. Try to get out there 4 times a week and get some light weights to do at home 2 days a week. If you are careful about watching what you eat you will see the first results quickly, though expect to settle into a slow and steady weight loss in a month or so.

Good luck. Once you start to see results and get in shape you will be truly addicted.