HTC M8. Can't explore files via windows.

My phone is connected over USB to Windows, where it is only recognized as 'Android Phone' under the unspecified tab. On the phone, no notification of USB connections is given at all, except that the phone starts charging. I've tried to enable MTP over USB, but I can't seem to locate the 'Use USB for..' menu anywhere. Searching for usb in the settings menu turns up nothing.