To read USB drives on the PenCentra, you need to install a driver. This one does the job nicely:
http://www.hpcfactor.com/hcl/detail.asp?hcdid=508&pn=1&mstrcat=17&s...
Download the CE 2.11 driver installer and run it on your PC while the PenCentra is connected via ActiveSync. Once it's installed on the PenCentra, insert the USB drive in the PenCentra and, when it asks for the driver name, type in
usbclik.