I reconfigured some PC's in my collection and used an old single core 3GHZ Celeron with SIS video card to run Windows 7. It will not support the Aero desktop, but with using the Royale and Zune basic themes, I got some great results as can be seen below. Below is the link for these great themes....
The Royale and Zune Windows 7 Basic themes are found on Tweaking with Vishal's website at:
http://www.askvg.com/download-windows-xp-zune-theme-for-windows-7/