On an internal mailing list, somebody asked why the thumbnail-based Alt+Tab interface in Windows Vista doesn’t show a little ✖︎ so you can close the window directly from the Alt+Tab list:

I tend to end up with a gazillion email messages all over my screen, so I need to do garbage collection from time to time. Maybe it’s my own fault for letting them pile up in the first place. The taskbar does such a good job of hiding the clutter that the moment I realize that I have too many windows open is usually when I hit Alt+Tab. I find that while I’m searching for the window I want, I wander through a lot of random windows I want to close. I don’t want to have to leave Alt+Tab to close those windows, since I’d have to return to Alt+Tab and start my search over. Why isn’t there a red × in the corner of each thumbnail so I can close them without having to break my concentration?

One of the developers replied with this answer:

When we originally added the new Alt+Tab to Windows Vista, we also included the ability to close, minimize, and maximize windows without leaving Alt+Tab. We had to abandon the feature, however, in large part because the new Alt+Tab runs inside Explorer (which is not normally elevated), and bad things were happening when we tried to manipulate elevated windows. There were other problems, too, such as trying to close a window that displays a “Do you want to save?” dialog.

Fortunately, these problems got worked through and resolved in later versions of Windows, so you can now close directly from the Alt+Tab. But this explains why it took a while.

If you’re still running Windows Vista (and really, huh?), and you want to close a large number of windows and closing entire taskbar groups doesn’t give you the granularity you need, you can hover over the taskbar button and click the the ✖︎ for each thumbnail you want to close.

You can also hit Ctrl+Shift+Esc to launch the Windows Vista Task Manager, go to the Applications page, multi-select all the windows you want to close, and click End Task. If you do it from the Applications page, then Task Manager will do the friendly thing and post a WM_CLOSE message to the window.

Don’t try this on Windows 8 or later, though. Ending a task from the Applications page will terminate it immediately!

Pre-emptive snarky comment: “The idiots in charge of the Windows 8 Task Manager didn’t include this feature in their redesign.”