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

I am using only thing remaining Office Standard 2010 and I am considering getting Windows 7. I have been shopping online and I have found Office 2010 Home And Business Activation Key and Windows 7 Upgrade. When I think of an upgrade, I think of it as something to improve Office Pro 2010 Serial I already have. Is this the case with Windows 7 Enterprise X64? Is it an improvement on Windows 7? If so, why hasn't the upgrade been integrated with the Windows 7 software?