I don't know why it happened, but my taskbar buttons were missing from my taskbar. You know, the little buttons that show you all of your open applications? If you're like me, you have at least 3 or 4 program windows open at one time. When these buttons are missing, you have to rely on the Alt-Tab trick to switch between windows.
A Google search showed me that this is a fairly common problem, and some of the solutions were not exactly easy... until I found the Taskbar Repair Tool Plus! This little gem (did I mention it's free?) took only a few seconds to download and install, and within 10 seconds my taskbar buttons magically reappeared! Hallelujah!
Now, on a much deeper, more philosophical level... had I not "learned how to learn" I would have had to pay someone to come to my house and fix this minor, but annoying problem. But because I knew what I was looking for, I was able to Google it and find an answer within minutes. This is one example of what it means to be a "lifelong learner" and what we need to be teaching to our students (and other teachers).
Thank you Kelly's Korner! The software will also repair a whole list of other Windows XP problems. http://www.kellys-korner-xp.com/taskbarplus!.htm