Yep Poser5 can read the PP4 runtime with no hassle, even if it's installed on a different drive to Poser5. I'm not certain 100% if there is a limit to the number of folders in Poser5 (haven't found it yet) but with multiple runtimes you can have a seperate runtime for each character which would cut down the number of folders you have to trundle through. Just imagine you've got Vicky & Mike in seperate runtimes you'd never have to go through 150+ folders of Vicky poses to get to that Mike folder you want, all you'd have is the Mike folders to go through :)