I tether my iphone 4s with my windows 7 laptop. However, when I try to tether with my windows vista desktop computer, it will not work. I have the latest version of itunes installed, but the Apple Mobile Device Ethernet driver will not install correctly. I get the message - "Windows cannot load the device driver for this hardware. The driver may be corrupted or missing. (Code 39)". Any ideas on how can get the driver to install correctly and allow me to tether?