If you ever wished you could take control of someone else's computer to help them fix a bug -- or if you ever wished you could show someone your screen, Team Viewer is what you need. It's a free, small program that allows you to see or even control someone's computer (with their permission). The screen picture is very clear and updates quickly.
I recommend using the first "Portable" version from this page:
Thanks to Rob Liaison for telling me about this!