You can install Poser any where you want. If you have space on the C drive just make a folder there outside of Programs and have at it. Once you install Poser outside of programs then you can install all the content to the Main Runtime inside of the Poser Program folder just like it was a version 6 or 7, before the UAC in Vista. I have the SR3 installed on my PP2012 and don't seem to have any issues. If you do setup the program outside of Programs make sure to look at each install option and select the ones that will make Poser think it is an older version.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13