a.Connect your Windows Phone to your computer by using the USB cable that was included with your phone.
b.Windows 8 users: In the Start screen, type "Device Manager," tap or click Settings, and then tap or click Device Manager.
Windows 7, Vista, and XP users: Click Start, right-click Computer, and then click Properties.
c.A window will appear with the name of your computer and a list of files. (If you don't see the files, click the name of your computer.) The name of your Windows Phone 8 should be listed under Portable Devices. If Windows Phone was incorrectly installed, it may be listed with a yellow exclamation mark. Or, it may be listed under Other Devices as a USB device or an unknown device.
d.Double-tap or double-click Windows Phone (under Portable Devices) or the unknown device to open the Properties window.
e.On the Driver tab, tap or click Uninstall.
f.In the pop-up box "Confirm Device Uninstall," select "Delete the driver software for this device" and then tap or click OK.
g.Return to the Device Manager window. Tap or click the Action menu, and then tap or click Scan for hardware changes.
h.Open Portable Devices, double-tap or double-click the name of your Windows Phone, and then click the Driver tab.
Note If you don't see your phone's name, tap or click the unknown device that is listed under Other Devices, and then tap or click the Driver tab.
i.Tap or click Update Driver.
j.Tap or click Browse my computer for driver software.
k.Tap or click Browse, locate the C:\Windows\Inf\ folder on your computer, and then click OK.
l.Click Next and if you're prompted, click Install. You may only be given a Close option.
m.After the driver installation is complete, close the open windows until you exit the Device Manager. Restart your computer if you're prompted.