First I'm computer illiterate. Is it possible that a monitor can slow a system down noticably? I had a Dell dimention (bottom of the line) running Vista that was painfully slow. I thought it was Vista causing the problem. Replaced that computer and hooked up the monitor to my laptop. Now the laptop(XP Pro) has slowed down considerably. Could it be the monitor?
No, not the monitor itself. However, the fact that the laptop is running any external monitor could. Just what is it doing that you perceive it as "slow"? Is everything slow on both computers or just one application?
Your monitor could slow your system down, if you dont have a dedicated video card then some of your system memory can be used for video. Motherboards with embedded video cards did that (remember 10 years ago when i was a student)