I frequently have 10 or more windows of the same application (e.g. Outlook, Word, IE, etc.) open at one time. Windows 7's new taskbar grouping thumbnail feature shows a preview of open windows (aka thumbnails) when you single-click on the taskbar group for that application.

But when I have over 10 windows open (more thumbnails than will fit horizontally on my screen), Windows reverts to a vertical menu. This is disconcerting since I need to train myself to deal with two separate behaviors and can never anticipate what I'm going to see when I click on a taskbar group.

Furthermore, I find the thumbnails more difficult to visually scan through (vs. the vertical menu) because only 1-2 words of each window's title are shown. Typically that's not enough text to disambiguate and help me find the right window.

I'd like to force Windows 7's taskbar grouping to always show a vertical menu (like in XP) instead of sometimes showing thumbnail previews and sometimes showing a vertical menu.

Anyone know how (whether?) this can be done?

UPDATE: BTW, I'm running the RTM version (build 7600) of Windows 7. There are apparently other solutions out there which work on earlier builds, but which don't work on the RTM build.