Here is a short list of some of the more valauble (IMO) WinKey combinations. OK, there are more shortcut keys than the following, but these are some of the ones I use the most that involve the mysterious "Windows Key". WinKey + D is nice when my desktop just gets too cluttered. WinKey + E is great when I need to browse my file system.
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Any time I can keep my hands on the keyboard instead of flying back and forth from the keyboard to the mouse, its a win-win.