Firstly in addition to the normal backup I made a duplicate backup on the new drive. I use a syncing program which verifies all files and I have trust in its ability.
In the folder view of PSu I simply pointed the directory to the directory on the new drive.
After about 10 mins a message announced that 1036 folders had been mapped, so the 45,000 images on the new drive were now seen by PSu. I had not expected this to be so easy or so fast.
