If you have recently upgraded to win8 you will find that some of the USB drivers we use for machine communications will not install. 
By default, windows 8 disables the installation of un-signed device drivers. 
However, you can override this behaviour by altering advanced startup options like this:
(You may want to close any open apps or documents first, as you will be closing  the PC down)
Move mouse up into the Top/Bottom Right corner and pick Search:
Then pick Settings, type Advanced… and you will the advanced options appear:
 
From the PC settings screen, choose General then scroll down and pick Restart Now:
 
Now pick Troubleshoot:
 
Now Advanced Options: 
Now pick Start-up Settings
 
Now hit the Restart button
 
You can now choose to Disable driver signature enforcement by pressing the key 7 or F7
 
That’s it, you will now be warned about installing unsigned drivers as you were in previous Windows versions instead of a complete failure to install.
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