Martin,
Please forgive my entering water over my head. You are already receiving support from one of my technical support heroes. And maybe I digress from your question ... but for what it is worth ....
There was a time when I rigorously deployed data on distinct drives to facilitate data backup, migration, etc. independent of program and system files. Perhaps we have similar thoughts in this regard. With most applications, I still promote this theory.
With ever-faithful Pegasus (for which I am always grateful to David Harris, et al.), my damaged brain is insufficient to remember the myriad technical details and motely administrative tasks of sustaining pmail data apart from pmail program files. Rather then forsake Pegasus for a come-lately email client, I allowed the remarkably compact, brilliantly crafted Pegasus code onto my data disk. My data disk does not mind the minimal intrusion. My diminished brain is no longer over whelmed. I can get on with my dotage.
If the details of porting an existent Pegasus installation from C: to X: interest you, better minds then mine can advise you. I think I copied the Pegasus directory branch from C: to X:, then edited some files, possibly pmail.cfg and pmail.ini to change every instance of "C:\program files\pmail\admin" to "X:\xxx\pmail\admin", and so forth. Maybe pconfig.exe will accomplish thise modifications, without need for manual edits. For convenience in Windows, I also added an appropriate shortcut into my quick launch bar. In any event, you can tweak a new, test installation without compromising your ongoing application. Be prudent in whom you trust for technical advice.
My suggestion is analogous to maintaining Pegasus on a portable, self-contained drive. This forum may contain suggestions for installing/maintaining Pegasus on thumb-drives, and such.
I admire your initiative, persistence and diligence in the programmer's eternal quest to bend machine to mind. I wish you the best.
BTW, as you probably know, transferring files via CD may yield read-only files. Pegasus requires write rights.