perhaps the easiest way is to first click on your C drive. You should see the various folders like Windows, Users and Program files. Before we go any further you need to click on 'View' to open up the ribbon along the top. You need to find a box marked 'Hidden items' and tick that then we can proceed. Once you've done that click on Users followed by your name. Look for a folder marked 'App Data' and open that, you should now see amongst others a folder marked local. Click on that and inside you'll find a file called 'icon cache', delete it and reboot. You should then find your icons restored to as they once were.