iphone and ipad not found during update

When I update my IOS software on both my Iphone and Ipad, as soon as the backup is complete and the device restarts for the update, it drops out of iTunes and the Apple USB driver disappears from the Windows Device Manager. So my device is stuck on the "connect to iTunes" display and it isn't recognized regardless of whether I restart the PC. Fortunately, my wife has a Macbook air that I can update the devices with, but I have to restore my backup from my PC because the air HDD isn't large enough to store all the backups for our phones/ipads. Once I upgrade with the mac, it can connect into the PC again. Anyone have any solutions for this?