Windows Explorer no longer displays the icon for my external USB drive. Device Manager tells me 'This device is working normally', but uninstalling and reinstalling the drivers hasn't brought back my icon. I use Avast, Spysweeper, A-Squared Malwarebytes, Spybot and Microsoft Security Essentials.
First, I suggest you cut back on all the security software. They aren't designed to work together and may actively conflict with each other and hamper PC performance.
The hard-drive issue could be down to several things. Try reinitialising it in Disk Management. Go to Start, right-click Computer, Manage, Disk Management. If the drive is listed there but described as 'Unallocated', there may be a fault. Right-click the drive and select 'New Simple Volume'. Follow the instructions given.
It's also possible that the drive has stopped working. To establish this, try using a different external drive or taking the disk out of its chassis and connecting it to the machine internally.