hi
I had exactly this problem after buying a 101 and installing the curie core
the fix is quite easy, in Device Manager right click on the device and select Update Driver
when the search for driver window comes up click on Browse, set the directory to C:/ and let windows search for the driver. When it finds the driver click the Install button and all should be well, on mine in Arduino Tools/Ports the new serial port will be visible, select it and your ready to rock
hope this helps and good luck
Dave