My SD card reader and USB ports have stopped working on my Dell Studio laptop running W8.1.

They still identify what's put into the ports and reader as the USB sticks light up and the computer goes bing when an SD card is put in, but they don't show up in Windows Explorer. If I put a cabled USB device into the ports, like the printer lead or a lead to the camera, these do work and show up in Windows Explorer.

Any ideas on how to fix this please?

Many thanks!