When trying to communicate about software techniques, it's often useful to display and share an image of one's own screen. There are a number of programs that support this function, including one or more that may already built into your operating system.
This page has a useful tutorial on basic screen capture functions in Windows.
Gina Trapani's blog has a nice tutorial on captures in Vista with an integrated MS utility (which, unfortunately, is missing from the Vista Basic version).
I've been using Gadwin Systems' popular 'PrintScreen' freeware for years.
Typically screen grabs are captured in .bmp (bitmap) format. I convert them to .jpg in GIMP or Photoshop.