Do you have landline with Comcast or just cable?   If you have landline from them, you can't buy your own modem.  You have to use their modem because they use their enhanced 911 sytem.  They won't let you get away with not renting it if you have their landline.

Edited By: Sham99 07/18/2010 8:59 PM. Edited 1 times.