Install ADT driver:
- Open PC settings
- Under General, look for the item Advanced startup at the bottom and click on Restart now.
- Now select Troubleshooting and click on Advanced options in the next window.
- Now click on Start settings and then click on Restart.
- A restart is carried out in the start settings. Here you can use the F7 key to select the entry Force disable driver signature.
- Once the PC has been started, simply attach the Android device of your choice and install the drivers.
- This start setting is only valid until the next restart is carried out.
- Install drivers e.g. for Nexus 4 http://forum.xda-developers.com/showthread.php?t=1995688 and for Nexus 7 http://forum.xda-developers.com/showthread.php?t=1809195 or see manufacturer's pages