Yes, you can transfer files to the 770, but only the memory card. So, you must have the memory card plugged in and then connect the USB cable to the device. XP will go through it's process of recognizing the device ( you may have to reboot as well.) After that, it looks like another drive to XP.

You will not be able to browse the device itself from XP, like you can with Smartphones/PocketPCs. You can only transfer files to and from the memory card.