There's a British TV show called "The IT Crowd" about how an IT department interacts with other departments in a large company. There's a running gag on the show where the IT workers answer the phone every time by saying, "Hello, IT--Have you tried turning it off and back on again?"
Overwhelmingly, the vast majority of computer issues (programs don't respond, internet connection drops, network folders stop working correctly, etc.) that come up from day to day use can be solved simply by powering down the computer and restarting. Some people seem to think of this as a last resort, whereas that is actually one of the first things I will do when I come into your classroom/office.
If at all possible, try to save any files you may need before shutting down the computer (however, if it's completely locked up, this probably won't be possible). Then, if you can't shut down/restart from the Windows Start menu, simply hold down the power button on the computer for about 10 seconds, or as long as it takes to shut down. Finally, press and release the power button to restart the computer.
This simple act of restarting all of the computer's core services may be all you need to fix your problem. Also, it can save me a lot of time in the troubleshooting process. It may even alleviate the need to contact me at all!