Do I really need "Parallels Upgrade to Win 7"?

I have just ordered Win 7( Upgrade). I need to know how difficult it is to replace my XP virtual machine with the Win 7 upgrade. Is it really necessary to buy Parallels Upgrade to Win 7 software to accomplish this? It has gotten very confusing for me as I am researching just what steps need to be taken to achieve this upgrade.
I am using Parallels 5. I would like to avoid reinstalling my Windows programs.

 

The system requirements say that "Parallels Desktop® for Upgrading to Windows 7" is not for virtual machines, only physical computers.
http://www.parallels.com/products/upgrading-to-windows-7/system-requirements/

I guess you should read http://windows.microsoft.com/en-ca/windows7/help/upgrading-from-windows-xp-to-windows-7

 

So let me get this straight. If I want to replace my Parallels 5 Windows XP virtual machine with Windows 7, I would need to do a clean install? This would mean re-installing all of my Windows programs.
Is it possible to just install Win 7 as a new virtual machine and share the currently installed programs and files?

 

Clean install. Seems like a headache, but it's worth it as you won't have upgrade issues that you see so many people here having.

 

So what happens if I am on my Mac running parallels with XP running and insert the Win 7 upgrade disc in the drive?