Is there a keyboard shortcut to close windows from the Windows 7 taskbar window selector?

looks like no - at least, without using an external program like AutoHotKey

List of shortcut keys from Microsoft

Steps:

1. WindowsKey+T
2. Left or Right key to get to the correct app
3. Up/down arrow to get to the correct app instance
4. Context menu key (right of spacebar)
5. C (for Close)

I found article, check this article .. maybe can help you

Here’s the full list of Windows 7 keyboard shortcuts or accelerator hotkeys available on the operating system level and also for several built-in application programs in Windows 7 .. http://www.mydigitallife.info/windows-7-keyboard-shortcuts-accelerator-keys-or-hotkeys-full-listing/

For keyboard lover, Microsoft has added several keyboard shortcuts, hot keys or keyboard accelerators to make navigation and usage of Windows 7, especially the new Windows Aero snapping feature easier by using keyboard. http://www.mydigitallife.info/new-keyboard-shortcut-keys-hotkeys-in-windows-7/

There is not a keyboard shortcut to do exactly what you want.

You might be able to get close to what you want with a combination of Alt+Tab (holding alt, tapping tab) or with Aero enabled the same thing with Win+Tab. To close the active program use Alt+F4, to close just the active window of a program use Ctrl+F4.

I hope that helps.