I have Poser 2012 saved to the programs folder on my C drive.  The Poser runtime is in My Documents folder which exists on my D drive, in fact all the downloads and temp files are also on the D drive as the C drive is an SSD.  All other runtimes are on the E drive, another physical drive, and any work in progress is on yet another physical drive, drive K.

I have UAC turned on and have done so since I purchased Poser 2012 on launch.  I have never hit a problem with either opening scenes or saving scenes so it all appears to work. That said I do have other programs also installed on drive D, leaving the SSD just for the most used programs.  All programs on drive D work without issue so I would expect Poser to do the same if installed there.

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.