Try this with it plugged in.
Open up a command promp with Admin Rights. (Click Start, Type in CMD, right click and run as administrator)
Type in each line and then press enter. The letter X will represent the Disk number it list.
diskpart
list disk
select disk X
clean
If it gives you an error here the SD card is bad. otherwise continue.
now click on start and type in diskmgmt.msc
you should find your 16GB SD card with a black bar in it. Right click on and it select new simple volume. Just click next though everything and see if it formats then. If it doesn't the SD card is bad.