They call it an Upgrade version because....

Because why? Well, if you got one because they are cheaper than the full version, and then you discover that to install it over the Win-7 RC you will still need to do a 'clean install' which doesn't save any of your own programs or tweaks, there's good news, Pilgrims...

And the good news is that an upgrade version really is just what it says, if you're using it on a system that already has had Windows 7 retail version installed. You can re-install using the 'upgrade' option, and it saves all your installed programs, your personal tweaks, and even that customized logon screen background you replaced the Microsoft version with. But you will need to go onto Windows Updates and restore all the updates for it, because for some mysterious reason, it doesn't save those from its previous incarnation. Can't imagine why not. Maybe Mr. Microsoft will explain that to us one day. And it all takes about 40 minutes. 

The image above was scanned from the box cover, and it also makes an icon for your programs folder, if you use IcoFX, which you can find here.