Here is a link to Kanguru's web site. They offer an upgradable thumb drive solution that allows you to put read and write to a SD card. No drivers required. Just hook it up to your PC, move some files to it, and then install the SD card into your Axim and away you go. Not as elegant as using the AX as a mass storage device, but it is a driverless alternative.
http://www.kanguru.com/microdriveplus.html