AutoPlay begins reading from a drive as soon as you insert media into the drive. Therefore, the Setup file of programs and the music on audio media start immediately. That behavior is very annoying as well as it imposes a security risk if there is any malware program stored in the device.
Microsoft has released a fix-it tool to disable or enable Autorun function. You can download the tool from here: http://go.microsoft.com/?linkid=9741395
To enable it back run this tool :http://go.microsoft.com/?linkid=9743275