Dunno if you're still needing the answer to this but i have the same phone and i do this;
Plug the phone in via the usb cable
Click start then right click my computer and then select properties
Click the hardware tab and then device manager
Right click the first line, usually the pc name then scan for hardware changes
I think it comes under the USB selection in that box
Right click the phone, may have an exclamation mark beside and select update drivers
Select Locate driver from file and folder or whatever it said
Then locate the driver and select it and that should be it