What is the difference when buying windows 7 from upgrade and full?

[GaryLK]

I doubt will work during using Microsoft Office Pro Plus 2010 Product Key and I am considering getting Windows 7. I have been shopping online and I have found Office Home And Student 2010 32bit and Windows 7 Upgrade. When I think of an upgrade, I think of it as something to improve Office Home And Business 2010 64bit I already have. Is this the case with Windows 7 Professional 64bit? Is it an improvement on Windows 7? If so, why hasn't the upgrade been integrated with the Windows 7 software?