You could try this! You'll lose everything but its better than having to buy a new phone!
Take the battery out the phone for a few seconds to make sure its completely off then plug it back in but don't power up the phone!
Hold the power button and the volume down button together and it will boot you into Hboot! ( Screen should be white with coloured letters )
Then you can use the volume buttons to navigate around the menu!
GO down to Recovery and hit the power button to select it!
Eventually a Red triangle with an exclamation mark should appear! That is you in the stock recovery!
You should then hold the volume up + down and the power buttons together and it should take you to another menu!
In here there should be an option to Wipe and/or CLEAR CACHE, press power to select the both!
There should also be an option to CLEAR STORAGE, press power to select this as well
Then select REBOOT, or just pull the battery and re-insert, then reboot.
if that doesnt work your in trouble and you'll have to find an official RUU with HTC keys and flash it through stock recovery! Im not to familiar with HTC's so i wouldnt be your best guy for that though!