Hey Sirat, welcome to IM.
I want to wish you good luck on your progress, but I have to tell you that the comments you made are a bit alarming.
You want to just exercise and not diet, because you can't diet successfully. AND you want to do it at home - do you realize how unlikely it is that you reach a goal like the one you have set for yourself with these MAJOR limitations?
First of all, I guarantee you that unless you get your NUTRITION in order, you will not have much success long term in your life, and you will keep losing and gaining (which is as unhealthy if not MORE unhealthy than just simply being overweight). If you can't diet successfully you need to explore the reasons WHY and address those first because ultimately, what you put in your mouth for the rest of your life will determine what you look like inside and out.
Secondly, you would have to exercise an obscene amount in order to burn off excess calories EATEN plus excess calories already STORED.
Third, chances are that if you have not been exercising, doing resistance training, the muscle you had four years ago is likely NOT there anymore under the layers of fat. Muscle wastes away from lack of use. It doesn't just sit there waiting for you to uncover it again. So even if you do 5 hours of cardio a day six days a week, you will lose WEIGHT but you will not find what you thought you had, tucked away somewhere.
Finally, an at-home program, to START is fine, but unless you have a nice gym set up at home, or someway to include heavier resitance training down the line, this is also unrealistic.
These are my suggestions to you:
1) As much as you don't seem to want to - face your issues with regards to food. Why are you unsuccessful at dieting? What holds you back?
2) List your goals as specifically as possible on a piece of paper
3) with your goals in front of you, write down specific steps you KNOW you need to take in order to reach them
4) set realistic milestones on the way to your ultimate goal - these milestones can be anything from going one week without falling off your diet, to losing 3 pounds, to losing one inch, to doing 15-20-30 minutes of cardio at 70-75% exertion without stopping... you decide.
5) keep a journal, either here on IM or privately if you dont want to share your journey with us.
6) find support locally - either by joining a gym, or weight watchers, or recruiting a friend or relative to go on this journey with you or at least hold you accountable.
How have you lost weight in the past? what did you do to go from 300 to 99lb? How long did that take?
Just stuff to think about....

Hi again.
I am an overweight person, on the continous cycle of weight gain and loss for the past 10 years...Have gone to 300 pounds and come down to 99 pounds am currently at 172 and going back to 300 pounds!!!! Want so much to be lean and trim, but lack the kick to get myself going. Also work full time from 600 am to 600 pm 4 days a week, so lack the determination to push myself more...Angry at myself, and want to start.
Have excellent muscles 4 years back, besides my calves and abs, everything else is lost in the huge masses of fat. Cannot diet successfully so want to work on an excercise plan that allows loads of excercise, but no diets!!
Please help if you know of a good at home exercise plan.
Cheers,
Sirat