upgrade - Can a key-less install be done with Windows 7 Pro from Digital River and enter later the product key for the Full version?

As explained below, I purchased a system builder Vista Home Premium (64bit) OEM install DVD, with free upgrade to Windows 7. However, I realized afterward that I needed Windows 7 Professional.

Can the ownership be transferred for Windows Vista Home Premium and its Windows-7 upgrade OEM DVDs?

Luckily I qualified for Microsoft's UltimateDeal student discount for Windows 7 Professional Upgrade. Microsoft customer service generously offered to send me at no cost a physical copy of Windows 7 Professional Full.

I just downloaded the Windows 7 Professional Upgrade from Digital River. The Full version will arrive by mail within 3-5 business days.

The customer service lady did not understand when i asked her if I'd be using a different product key than the one from Digital River and told me to wait for the copy she send me today.
I'd like to start the custom clean install now that I prepared for it and it is going to get busy in the next few days for me. I read somewhere that a key-less install allow you to use the installed Windows for up to 30days (i.e. as an evaluation. By then, I would have received the Full install DVD and product key.

Can I do a "key-less install" form the DVD burnt with the ISO image I got from digital River and not activate it until I receive the product key for the Full version?

Regarding the Windows Home Premium OEM (64Bit), I only installed and activated the Vista version but won't install nor activate the Windows 7 OEM I received as a free upgrade from Vista last October. I understand that OEM Windows are not transferable to another system.

Is it still possible though to install the Windows 7 OEM and activate it on a different system or is it a loss and a waste?

Thank you very much for clarifying these two points.
Donat

Answer

Yes, you can do a Custom Install and enter the key later. You have 30 days to activate an installation of Windows 7.

The first system you active an OEM version on the only system the key is legally allowed to be reactivated on. So if you activate it now, and then try to activate it again on a different system later, you are breaking the terms of the EULA.