It’s worth mentioning the “Not Responding” issue in it’s own post.
Windows 7 introduced a new feature where if the system doesn’t get a response from a window for a certain amount of time, or number of polls, then the title bar of that windows displays the message “Not Responding”. Users are able to click the X in the corner to close the window. THIS DIDN’T HAPPEN in Windows XP — you just had to wait for the window to come back alive or you went into Task Manager to kill it.
This feature has had the unfortunate effect of making users close the app too soon instead of waiting for it to finish.