Are you in a classroom setting? Does each student have their own computer to use in class? If so, there is no better way to learn than by doing. What you might do, is change a setting or mess with something different on each computer and give them all a certain amount of time (15 minutes or so) to try and fix it. Its okay if they don't fix it, but at the end of the 15 minutes, demonstrate what the problem was on each computer and show them how to fix it. Better yet, show them where to find the information that tells them how to fix it. If they are involved in an interactive activity, it might help stick in their minds better.
I would guess that if they are doing a lot of Windows troubleshooting, your helpdesk probably uses technet and other such resources. Do a virtual troubleshooting session, where you come up with a known problem and act out a phone call situation and the students have to look up the solution and communicate it to you as if you were on the call. We use to do this when I worked in a call center. It was kind of fun, because the students got to use all of their resources, including each other.
I would recommend that if they don't have this knowledge already, it would do them a lot of good to understand basics about computer hardware and how Windows interacts with it. A good book for very basic computer hardware knowledge (what is RAM? How does it communicate with the processor? etc.) is "How Computers Work." It won't get them ready to design circuit boards, but it will fill in some of the gaps if they don't have much computer hardware knowledge. Its full of good pictures which describe how the different components work together.
I hope some of that helps.
