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#11
The key is not reuseable since it becomes locked to the first mobo installed upon. But like all Windows 7 you can reinstall it as often as you want on the same machine using the key.
Had you asked we could have told you that the path to Upgrade within Win7 is by using Windows Anytime Upgrade - How to - Windows 7 Forums which offers a considerable price break. I see Pro Anytime Upgrade version on the web now for $60.
This process involves only inserting the upper version Product Key into the lower version to unlock the extra features which are already there but hidden - since it's the exact same OS otherwise.
If you have the opportunity to take it back then you might want to do that, or if you haven't done the reinstall yet you can try inserting the key since Anytime Upgrade will work with a retail Product Key - and Builder's OEM is a retail SKU.