ok, so i'm assuming that you can access the SD card from the PC. As long as you have these two devices in device manager you're all set:
Under "Ports (COM & LPT)"
->CASIO C771 USB Virtual Serial Port (COMX) 'X' is a number
Under "Universal Serial Bus controllers"
->CASIO C771 USB Composite Device
If you have debuging on (which IMO you always should) under "Android Phone"
->CASIO C771 Android ADB Interface
If you plug it in as USB mass storage under "Disk drives"
->CASIO C771 Storage USB Device
If you un-installed the MTP Sync App and connect it as MTP Sync, that will cause the device to be "unpluged" as well.
If you have the first two, and the others for their respective modes, then you are all set and it is "normal" for the device to say it is unplugged if it is not.
Hope this helps