Following up this post I decided to go ahead with the order.

MS then tells me I will have to do a clean install rather than simply download the upgrade.exe since I'm using xp (for an additional $14 through the post). That's well and all, and since it's kind of necessary, I purchased the $50 license as well as the $14 CD.

After I checked out, I got redirected to the download page, which lists two options:

1) EXE - for upgrading with compatible OS

2) ISO - for clean installations.

^ BUT THEY DON'T TELL YOU THIS UNTIL AFTER YOU PAY NOW DO THEY?