With Vista, an iPhone supports syncing contact information with Windows Contacts, Outlook 2003, or Outlook 2007 and calendar events with Outlook 2003 or 2007.
You need to sync the Palm Desktop or your Palm with one of these supported applications.
This is possible with a Mac so I assume the same is or should be possible with a Windows PC. I can't give you detailed instructions, but maybe someone with a Windows PC running Vista who has done this will be able to provide you some detailed instructions.