You can still ask IPB if there's a chance they can convert your board, although they might charge 60 dollars for it.
Otherwise, you can look around and see if there's other board software you can convert to that there also exists IPB convertors for. A few months ago I converted our board from Snitz to phpBB and then directly to IPB.
I'd take backups of everything and run tests on installed backups first though, check that everything is going to be working fine. Don't experiment on your live board.
Doing the conversion from the beginning and on your own, is going to take a lot of time.