I'm having the exact same problem and would like to find a solution. It's rather remarkable that such a straight forward procedure would not be available. At the minimum it's amazing that there is not a way to listen to the voice memos through palm desktop, or just the PC. All we have are these '*_Vpad.pdb' files.
Finding them was even a bit of a chore. If anyone is looking for where their voice memos get backed up to... it's in a folder called "Backup" that's under a folder with your treo's name (abbreviated) which is in your Palm Desktop install folder. For me the backup files are at:
"c:\program files\palm\TreoJ\Backup"
I found one hack recipe for getting those voice memos playable on your PC:
Check this out.
http://palmaddict.typepad.com/palmad...erring-pa.html