Homemade DVR with Cablevision?

Cablevision in CT recently decided to scramble all of their channels, and now you cannot receive cable without an iO box. I have an HD box and the ability to build a homemade dvr out of an old computer. Is there any configuration or software or anything that will allow me to use a homemade dvr in place of (or in conjunction with) the HD box from iO? I don't want to pay cablevision an ungodly amount of money for their DVR.