Frank J. has noted in his X51v blog that he has been unable to sync Microsoft Access database files with his handheld using WM 5.0:

"So I contacted one of my fellow developers, a specialist in databases, and he has informed me that currently ActiveSync 4 can’t synchronize access databases. I should point out that ActiveSync 4 still not officially released by Microsoft. And when this happens, a module is probably going to be released to allow the Access Databases synchronization, but this has not been officially confirmed either."