If nothing else works - I have done this on several machines.
1. Do a fresh install on the new drive. Run the Pegasus installation download v 4.63
2. Then run once but just put in minimal data. Check the location of the Home Mail Directory-make sure it is correct, then close.
3. Then, copy from old location ONLY the \MAIL subdirectory to the new, assuming it goes inside \PMAIL or whereever you put it.
4. Run again - and rename the home mail directory location if nec. Should keep everything. And I mean everything, settings, fonts, window sizes etc.
May not be the most elegant way to do it, but it has worked for me many times. Let us know.