The offer let's users move from the barren Windows 7 Starter edition to Windows 7 Home Premium for only $49.99, which is $30 off the standard rate of $79.99. Additionally, those running Windows 7 Home Premium can upgrade to Windows 7 Professional for $79.99, or $10 off the usual $89.99.
Professional has many features missing in Home Premium, especially for businesses – hence the name. One such feature is Windows XP Mode, which grants Professional and higher editions to a fully licensed virtual machine of Windows XP SP3 – a nice touch if you're having trouble with stubborn software that hasn't been updated to work with newer Windows operating systems. Another particularly useful feature missing from Home Premium is the ability to host a remote desktop connection. You find a full comparison chart of the different Windows 7 editions on Wikipedia.