In order to use an upgrade version of Windows 7 you must have a previous version of Vista or XP installed first on the machine. You can still perform a clean installation with this method.
I currently have Windows 7 RTM on my computer. Last summer, I ordered Windows 7 Home Premium Upgrade when they were having the deals (I got mine for $49 from Sam's Club).
I've been putting off installing the Retail 7 because I want to do some upgrades to the machine and don't want to hassle with the Microsoft Activation over and over again.
So, I'm ready. I've got a new mainboard, two new hard drives, a new solid state boot drive, a new blu-ray drive and some more memory.
I suppose I could set up the machine, re-install Vista and move to the Retail 7 from there...but I feel I'm missing something. Of course, I'd like to do a clean install of the Retail 7, but not sure that's 'allowed' by MS.
Here's what I'm thinking: Just install all the components under the existing RTM and start it up, no matter how wobbly it is, then immediately upgrade to the Retail 7, specifying the new Solid State as the install drive, then go back and clean out the old RTM drive/directories.
Do you think that'll work?