Were you able to manually install postgres?
What drive are you attempting to install it to? If it is not the C drive then would you be able to install it there?
Also, follow the steps in the link provided by l.vanagteren and use a local admin to try and install.
If all of the above fails you can look in the install directory for a Avalanche**.Install.log to see where it is hanging..
You could also look for the bitrock-install.log. This is the postgres install log, and is located in the User\AppData\Local\Temp folder.