You can flash the RUU with the phone in fastboot. Plug it in (you should see fastboot USB in red), have the file in the PC, open a cmd session as admin and navigate to where the PD98IMG.zip file is and then type:
Fastboot oem rebootRUU (you should get a black screen with silver HTC)
Fastboot flash zip PD98IMG.zip (when you get the okay in the cmd screen, ignore the green bar in the phone)
That will flash the file without using volume rocker. Hope it works...
Sent from my Inspire 4G using XDA