How can I disable a cable modem on boot?

I must boot into safe mode, disable my 1 way cable modem,(via the control panel/system, then reboot, to use my PC. How can I always disable on boot up, I think this will solve part of my problem. This happens a lot !! It is a one way cable modem and has always done this. It also locks up at night even after I have disconnected the modem online.Win98se.P4 1.5 256 ram