This is my scenario, and I've yet to test it with any other setup. I've got 2 partitions, first is XP, second was vista. Back in January when Windows 7 first came out, I figured I would need a blank DVD like the instructions said. Instead, I decided to try and mount the iso and see what would happen. It started the windows 7 set up process, but it said I was ineligible for the upgrade but it could do a clean install and all of my files would be moved to the typical Windows.old directory. So I let it do its thing, the set up went off without a hitch, my computer restarted as if I had a physical disc in my drive and continued the set up process every time it restarted.
Long story short, You don't need a blank DVD. You just need knowledge of how to mount an .ISO
I apologize if this has been mentioned before, as I know I'm not the only one that knows this.
Edited by Uraiser, 12 May 2009 - 03:22 PM.