My Nexus 4 is recognised as a Nexus 4 in Device Manager with a yellow exclamation mark on its icon.

When I installed the USB drivers for it, the yellow mark went away, and Device Manager said that the device is working properly. However, it is not appearing as a portable device or removable drive, and I cannot access the files on the device.

What am I missing? I'm running 32-bit Windows XP SP3 .