If you live near a store, you can bring in any Windows 7 compatible PC and the Store techs will do a clean install of Windows 7 (NOTE: If your PC already has WIndows 7 on it, you're good to go - no new license is required!

Meaning, if you bought a Windows 7 computer somewhere else (with crapware, etc.) you don't have to buy a new license--they just clean off the crapware for you and install their stuff.