Re: Windows 8 won't install game properly.
It's not Win8! You should ditch the Gamefly version (get your money back, if possible).
I've installed both DAO and DA2 (both retail disc and EA/Origin versions) on my Win8/64-bit rig with no problems. Did it several times (Consumer Preview in Feb 2012, then Release Preview in June 2012, then Win8 Pro in Oct 2012.) No problems with any version.
Even if you can't get a full refund from the vendor, you can probably still get the EA/Origin download without having to buy the game again. Install the Origin client, then contact EA Customer Service (http://support.ea.com http://help.ea.com) and Chose "Contact Us - Get Back in the Game". Explain the situation and if you have your CD-Key, they should be able to authorize the d/l to your Origin account.