Hey,
I found out how to connect the iAudio X5 to a PC without having to use the silly subpack. Without Rockbox and just the original firmware it's done simply by connecting the player through the USB HOST port on the device to your PC. If you dual boot, it's done by booting into the original firmware and then connecting through the USB HOST port. In either case, sometimes Windows XP need to install software and reboot first. On Linux, my computer just connects to it, but then an icon apears on my desktop of an external hard drive, whereas when I connect through the subpack, a icon of an mp3 player appears.
Hope this tip is of use to you.
Regards, Daan