I tried for weeks everything to solve this problem, and this is the only way it worked for me.
Go to Control Panel - Hardware and Sound - Devices and Printers
Down there you will find your iPhone. Right click on it and click Properties.
Click Hardware and again Properties. In General click Change settings.
Now go to Driver and uninstall your iPhone. After your iPhone was uninstalled plug it again. It will install again and the computer will regonize your iPhone.