Folks, this IS working for me...
After downloading and attempting to install the Digital River file (which quit near completion of installation) it left a folder on my desktop with the necessary files inside -- they are completed, even though you get the erro. If you then use the USB Key install method here:
How to Make the Student Discounted Windows 7 Upgrade Bootable | Notebooks.com
... to do a "custom install", you then WILL be able to do a FULL install over the top of ANYTHING... be it XP, Vista, or even NO operating system (I had no OS on my new build, and it worked). I formatted the HDD, though.
And yes, my Digital River product key worked just fine. No issues. I'm up and running. Took me 5 hours of attempting to burn ISO disks, hunting sites, and pulling out my hair until I found the above USB key method, though. FAR easier than command line typing and burning DVD's for boot that never worked.
A couple of notes: I had to set my computer's Bios to boot from USB first in the boot order. Also, once installed, I had to pull out the key because after reboot, it attempted to reinstall Windows 7 again before completion. If this happens to you, just cancel out of the reinstallation, pull out your key, and reboot to finish.
THIS IS WORKING NOW!