I had AP 2.7.13.2714 installed and running just fine. I d/l'ed 2715, and tried to install it after uninstalling 2714 and rebooting. I removed c:\python27 completely.
All options (Typeical, Custom and Complete) immediately exit with an error and no system changes. I d/l'ed another copy, and it is identical to the first copy.
I obtained another copy of 2714, but it likewise ends prematurely with an unknown error.
Any suggestions? There is plenty of disk space, so that's not the problem.