I'm not familiar with 'Incredible Mail'. Can you transfer the Incredible Mail contacts list to your Windows contact list for Windows Mail? iTunes will sync a Windows Contact list to an iPad contact list, so the problem is simply (?) one of transferring the Incredible Mail contacts list to that on your PC or Mac. Can you export Incredible Mail's contact list as a 'CSV' file (comma separated variables)? If so, then Windows Mail can import it and put it into the Windows Contact list.
Most mail programs can handle CSV file format - it's the standard way of manipulating these files - so I'd expect that Incredible Mail could too.
Let us know if you have any success or, if not, we'll try to think of something else.
Good Luck
Tim
Scotland