Quote - Definitely put the Poser runtime on an external drive.  App on C:, runtime on external (R: or P: seems like a logical choice.)

Start -> Run -> diskmgmt.msc is what you're looking for to force Windows to never change the drive letter.

 

Thanks for all the help folks. gennenburg's suggestion seems to be the easiest way. Install Poser on C: and the runtime on the external drive, during installation of Poser. I can also put all the downloaded content on the external drive so it doesn't get lost if the PC crashes at some stage.

One question gennenburg, in diskmgmt.msc I don't see an option to not change the drive letter. What do I click to see that?