How is it possible to run Wordpad by just typing its name even though it isn't on the PATH?

Raymond Chen July 25, 2011 Jul 25, 2011 07/25/11

In a comment completely unrelated to the topic, Chris Capel asks how Wordpad manages to run when you type its name into the Run dialog even though the command prompt can't find it? In other words, the Run dialog manages to find Wordpad even though it's not on the PATH. Chris was unable to find anywhere I discussed this issue earlier, but it'...