One thing I notice, especially being on dialup, is that applications like Norton (3 months free with computer) update without indicating they are downloading, and there seems no obvious way to turn them off if I'm trying to download something more important to me. The only way i can find out what is downloading is to check the task manager to see what's running, and the only way I even know to check is if my connection is slow and/or the computer is making louder noises than usual.

The Windows updates themselves can be stopped and even refused easily.