I am using Poser since version 2 and never install it in root partition and never have problem even i import Poser files in DAZStudio pro 4,5, Vue infinite 11  or Carrara

Now i have Poser pro 2012 installed in E: and DSON file with genesis working ok .Some preferences files are saved for example in c: users folder  but all the majority of the soft and data are in others partitions 

I have older runtines in D: and E: and  indicate to Poser  where they are and have no problem when i load the pzz or figures or props or poses

I prefer to keep my root C as small as possible for more fast backup of it And now i have an SSD  with not as space as my older C hd

You just have verify and set correctly your soft parameters correctly 

I am also using Windows  pro 64 bits