Unhappy htc one dual 802w not detected by PC When connected via USB

Hi,
i bought htc one dual 802. its running android 4.2.2, software number-2.19.401.1
when i connect through usb, the phone just charges and nothing else happens. due to which i cant browse the contents of sdcard or on board memory.
Please can anyone guide me to make this work properly, as i cannot connect to pc for rooting/updating.
i hav istalled htc sync manager on windows 7 64bit pc