Search the net for "Windows UAC", and read all about it.
Windows likes apps to be installed in programm Files.

It prevents end users to write there.
So all your own stuff goes into your shared documents folder, including the PP Runtime..
When installing Poser, it installs 2 runtimes.

The first one in Program Files "FOR ITS OWN USE....."
And a second "end user Runtime"  ina location of your choise, but NOT in Program Files folder.
You can put it on an external disk, in your public folder, whereever you like, but NOT in Program Files.

If you do? Windows will indeed double the content in a "virtual folder", to prevent you to write in Program Files folder.

Search UAC, and read all about it. Poser is just complying with the Windows 8 requirements.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!