It sounds like you're running Poser off your external drive, which ought to work fine (I'm doing that with all Poser versions from Poser 4 and up to PP2010)

But did you reinstall Poser? I noticed that AT LEAST Poser 8 and probably (IIRC) Poser7, really likes to be installed on the computer to run properly. Earlier versions ran fine just from executing the e.e (I've - as a test - run Poser 6 from both an USB flash drive and a CD - both works!)

Try (re)installing Poser. It won't mess up your already installed content - and if you're worrying, install the Poser core files to the new INTERNAL drive and link all your old runtimes,

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.