...Use, Test, and true Cancel gadgets on preference windows.
Apply doesn't count. It's just an OK gadget that leaves the preferences window open. Cancel? They should just change that to say Close. Opening a preference window, making changes, hitting Apply, and then hitting Cancel should revert to the settings before the preferences were opened. It doesn't. It's largely useless.
Just for example, my father has hearing and vision problems. When he visits and wants to watch a movie, I turn on subtitles and set the subtitle font size to something ridiculously large for him. If I forget to change the settings back to normal, my wife won't watch movies because subtitles ruin the show for her. She's not savvy enough with tech to change the settings herself*, so she just does something else instead.
There are many other reasons to include gadgets that promote experimentation with settings. But for some reason, Microsoft deems experimentation too dangerous for their userbase...I guess.
*I've tried teaching her, but it's more than she cares to learn. You know how that goes I'm sure.