Scenario: I'm copying a couple of large files from a DVD onto my desktop (Windows 7 Pro, in case that matters). After a while I realize that it is going to take too long time, and I press "cancel". The copy dialog changes and says "Canceling...", and then nothing happens for a long time -- several minutes, long enough for my patience to run out.
Why does it take time at all to "cancel" a copy-operation? What is the OS doing or waiting for?