If you are new to exercise, you want to start lighter, to avoid injury and crippling fatigue. Start by walking, or hiking for a half hour every day, or an hour, every other day. Do you have a body band and light weights? Even fifteen minutes of resistance exercises or a very light weight routine (check youtube or your library for free instructional videos) every day, in addition to walks can be very effective and help you build up strength and endurance to tackle something strenuous, like P90X. Give it at least a month with the walking/hiking/light resistance stuff, before you jump in to something so taxing.