Try and recover your phone by downloading an official file from the htc website..
or there might be a similar thread here telling you what to do ..
this should reset your phone so that you can then start again ..
Edit ..: this is the guide you should be using.. the top couple of lines pretty much explains that you need to flash the official file ..
Have you tried booting without the sd card. Sometimes the SD card corrupts and that triangle shows
also try holding volume up + the power button at the triangle screen and select reboot now if that option comes..