The USB Mass Storage Controller driver enables Windows to communicate with USB storage devices, like external hard drives or flash drives. If it's missing or outdated, you might face issues accessing these devices. To install it, you can go to Device Manager, find the device under "Universal Serial Bus controllers," right-click and select "Update driver." Choose "Search automatically for updated driver software" to let Windows search for the right one. Alternatively, visit the manufacturer's website for a specific driver. Would you like help with a particular device?