It is the same password you use to unlock the device. Check caps lock, etc... but it is the same one. If you are approaching your number of tries, unplug it and lock it then unlock again with your password to reset the number of tries.
This is to allow your PC to use your media card (SD card) as a drive. You do not need to enable this but you will have to enter the password on the device to allow your PC access to it. The prompt on the PC side is also the same one as your unlock password. This is required for desktop manager to access the device and device memory.
Treat your password like your toothbrush. Don't let anybody else use it, and get a new one every six months.