Can a digital cable box be purchased from a store?

I once temped for Scientific Atlanta repairing those type of boxes. The reason another box won't work is because there is a chip inside each box that provides an identification resource that not only determines which channels the box will tune in for you, it provides pay-per-view information so that you can be correctly billed for the viewing. I mention the details only to tell you how fervently some people are, about getting a service without paying for it. We would get boxes in that had been run over by cars, burned, smashed with a sledge hammer - you name it. The chip was so protected that we could almost always remove the chip, put it into a working unit and still bill the customer for the pay-per-views. That chip is the same sort of thing that is in your cell phone that gives you things like your telephone number and carrier. To attempt to modify that chip or use it without paying for the service is quite illegal. That is not to say, however that Time Warner might be willing to allow you to buy your legitimate boxes instead of lease them. Only that chip/card would then belong to them. You'd have to ask them that question.

SOURCE: http://www.indeed.com/forum/cmp/Time-Warner-Cable/Can-you-purchace-your-own-cable-box-use-it-w-your-cable/t19744

Hope this helps