Installing Win 7 on Paralles on a Mac

Question

I had a Laptop with Win Vista on it, later I bought a Win 7 to upgrade, on the box it is saying Windows 7 Home Premium, on Top Left corner says UPGRADE designed for Windows Vista and on the back of the box it says if you want to upgrade from WinXP, you should first backup your data and then select a FULL install, SO what I get from this is that Ok the Win7 CD I have is a Full version, the whole upgrade thing means you don't need to BACKUP your data if you are upgrading from Vista,....and well it did the job and worked... Later I installed Linux Ubuntu on that lapotop so I am not using that Win 7 anymore and now I have an iMac and installed Paralles to run Windows on it too, I started with installing Windows and this is the message I get and installation stops. I am clueless what is going on... Here is the screen shot of error I get:

Answer 1

To install an Upgrade version of Windows 7, you must install it over a genuine copy of Windows. In other words, even if you choose to do a clean install, the Windows 7 Upgrade installer must first detect a valid Windows license already on the drive, virtual or not.

This is why it worked the first time (you had Windows Vista installed), but does not work now (the virtual drive does not have Windows XP/Vista installed).