On the device, Access format files don't appear to be supported by anything so perhaps would not be a good option. For me, SQLite seems to be a good choice as you can just copy the files between desktop and device.
You can create a single program on the desktop that opens both Access and SQLite at the same time - but with not with B4ppc. I use a VB6 program to synchronise with my original application (also VB6). Once written, it is now a quick process to have the data ready for the ppc and visa-versa.
There are several, but this free VB wrapper from
datenhaus by Olaf Schmidt makes database files that are totally compatible with SQLite as used by Basic4ppc.
Regards,
Geoff.