I have copied my images from my PC formatted external drive to a MAC formatted external drive. I then tried to use a copy of my last PC-generated catalog. However, the catalog cannot locate any of the images on the MAC external drive. When I select the correct image on the MAC external drive, I get a message saying the photo is assigned elsewhere. I am very confused about this; what is the recommended way to accomplish what I am trying to do?
You have to tell Lightroom the exact disk name and folder to find your photos.
See this document for instructions, particularly Figure 4 and associated text