Also, do you want the files to remain on the portable drive, or do you want them to be copied onto an internal drive on the HTPC?
You mention a portable drive and a HTPC. You also mention a laptop... Where does the laptop feature in this puzzle?
At first, your information suggests you are connecting the portable drive to the htpc, but are then having issues importing the files from it. We are going to need more detailed information about what you want, and what you have tried thus far to achieve that...
-marko