You should be able to use a regular command prompt, but you'd have best luck using an administrator mode command prompt. (right-click and choose Run as Administrator). You should also note that it will temporarily disable Aero before running the test, but don't worry, it will re-enable it after.
Here's some mini screenshot examples for your enjoyment, the real thing will run fullscreen. Try the command right above each one to see it on your own computer.
winsat aurora
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winsat d3d -texshader -totalobj 15
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You can check out the complete post here.