The setup code for Scientific Atlanta is 00877.

A Comcast remote with a red OK/Select button requires 5 digit setup codes, and the leading zero implies that the setup code is for a cable device.

Make sure after you enter the setup code that the remote blinks twice. That indicates that it recognized the setup code. When you were entering 4 digit setup codes, the remote wouldn't have accepted the codes, and would retain the exisiting setup code.

Also see Universal Electronics website for Comcast setup codes .