I'd also start swimming, or bike riding... Running will probably hurt you more than help you at this point, but once you get down to a better weight you will be able to run without potentially damaging your knees.
I'd also try to find something fun that is also good exercise. Swimming is usually pretty enjoyable, and it's actually one of the best things for losing weight and works out pretty much all major muscles. If it's fun and enjoyable, it makes getting ready to exercise much more tolerable, instead of being something you dread.
Also a good diet is always really key. There's a few things you can do that help and are pretty obvious.. Cutting out soda's and junk food, drinking skim milk, etc, but I'm sure that's not something you need help with. Whatever is easiest for you is usually best.. You want to eat about 1800 calories a day, (600 per meal, three times a day) but you can break that down into 6 smaller meals, or 3 meals at about 400 calories and then three snacks that are 200 calories... That way you can still snack a little, and that usually helps since a lot of people form snacking habits. You just have to be careful not to overeat. I usually plan out my meals/snacks before the week, and that allows me to have things set aside.. But I do that mostly so I'm not sitting there stumped 30 minutes before dinner without a clue what to make.
You can also join weight watchers for men... I have friends who do that and they love it.. It lets them still eat, but it balances out really well, most say it's one of the easier diets they've been on. But if you don't want to pay for those, it's not too hard to write out meal plans each week.
Good luck though! It's always hard at first, but after a few weeks it'll just be part of your daily routine and it's much easier.
