Do you have any interest in joining a gym? You have to be pretty self disciplined to work out at home, and be consistent with it. Videos like P90X help, but a lot of people slack at home.
I don't really know much about Atkins, but it seems like your basic ketogenic diet. They are good for short term fat loss, but unhealthy as a permanent lifestyle change. The bottom line is calories in versus calories out. Eat better foods in smaller amounts, workout more, you'll lose weight.
Of course I would say to quit smoking, but it's not necessary if you really don't want to. It's just going to make things harder. My friend lost 100+lbs over about a year, and he smokes a lot. He also works really hard, and is diligent about being in the gym.
Once you get a little more used to lifting start getting serious. Heavy compound movements build muscle, require more cardio effort, and burn more calories. If you are sticking to working out at home get a proper Olympic barbell set. You can do tons of stuff with just a barbell and plates, and if you have a bench it's even better.
For cardio the best thing you can do is very high intensity work. If you are really overweight it will take time to work into this.