Do the following steps in your target Windows Server 2008 x64 box.
To get the sidebar,
Now to get the Aero, assuming your graphic card is sufficient
Then spend the next hour to add/remove all the gadgets you like/dislike, which is the fun part. After all is done, here's what a Windows Server 2008 desktop may look like.
I just did something I’ve been meaning to do for a long while: re-tooled my laptop with Windows Server