Travel Technology - Why the ^+%#$*& won't my screen saver kick in?

I've got two machines, both Windows XP. I can't get the screen saver or power settings (shut down HD, etc.) to work. One uses Norton, and one uses McAfee for virus. Everything else appears to be okay. The screen saver will start if I haven't logged in yet, but once I do the machine stays on. It's annoying because my older machine has a loud fan that stays on.