Here's two screens.
http://imgur.com/a/mme2U
Basically (for those who haven't seen the installer in a while) once you start it up, it throws up a background of Firiona, you get a warning about anti-virus (I've tried all this with mine off, so that's a no-go), another screen, the Terms of Agreement, and finally you choose the install location. Then you get the loading bar in the first picture, which for me sits there and does nothing for a few seconds before the error window pops up (second picture). Closing this or hitting OK will terminate installation.
I have a theory that it's not the destination that's getting access denied but the files on the CD (I'm using a .iso with DT). They're in my default Downloads folder, so I don't think moving them around would change access priveleges.
Anybody have a clue what to try next?