Why is Windows Internet Connection Sharing not working?

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Currently my Windows 7 laptop computer is hooked up to my Windows Vista desktop computer with a CAT 5 cable, as to share internet. For hours I've been trying to find a way to connect the desktop PC to the internet, but even after following the same instructions from different sites over and over, my desktop cannot connect to the internet. I know it's possible, so what am I doing wrong?

Pics:
Windows 7 Network and Sharing screen: http://i.imgur.com/o9GUc.png
Windows Vista Network and Sharing screen: http://i.imgur.com/nGKwC.jpg
Windows 7 Internet Connection Sharing: http://i.imgur.com/2Vq48.png