Sentryl/Sebtryl,
Doof's steps are exactly what you should do. I'm not sure which part you didn't understand, so I'll go through them.
>1. Copy all of the *.jmd" files from the "J River\Media Jukebox\Data" folder on the primary system to the "J River\Media Jukebox\Data" on the secondary system.
This is self-explanatory.
On the secondary sytem:
>2. Open up the entire library in File Properties and go to Tools->Find & Replace.
>3. Check the box for "Location"
Open Media Jukebox on the secondary machine. All your files should be listed, but if you look under the location column, they should all be in the wrong directory. You have to change the reference to the drive.
>4. Enter "D:" into the "Find what:" box (no quotes).
>5. Enter "F:" into the "Replace:" box (no quotes).
>6. Click Ok.
I haven't tried these steps, but they look simple and right.