Go to Control Panel/Administrative Tools/Computer Management. Is it showing up ? If it is , hover over the drive number in the Computer Management screen and right click. Select properties.
What does the status say ? If it is good, at the bottom of that pop up window is a Select usage selector. Is it set to Use (enabled) ? If not enable it. Probably not that simple though.
If it is already enabled and status says good you can try the troubleshooter tab on that propertes popup. you can also check you driver and roll it back or update through the driver tab.
