For everyone who isn't familiar with how things work regarding Comcast equipment and buying/selling it, he're some advice. Don't.

The equipment Comcast uses only works on the specific account it is assigned to, and none other. For it to work on another Comcast account it has to be returned to Comcast where they reset and reprogram them to go onto another account. This is NOT something that can be done at home.

While it may seem like a good idea at first to purchase your own digital cable box, keep in mind that in reality, when you buy it, it simply will not work, and even if a Comcast technician shows up at your house to do an install, he will not be able to make it work.

If you are thinking of SELLING Comcast equipment, also keep this in mind: Comcast only rents these digital boxes out to people, and does not sell them. That being said, they are still technically owned by Comcast. If you are selling off the digital box from your account, Comcast WILL charge you for it! The amount charged is also quite a bit more than you'll get for one of these off Ebay.

So all in all, the best idea is to just not bother. If you want to get a digital box for Comcast, talk to Comcast about it, and they can take care of you. Don't waste your money buying something that simply won't work.