You can download the ruu from rootzwiki. It is an older version but it should get you back up. How to use the ruu.
Find the HTC fastboot drivers for windows and install. Download ruu file.
Put phone into fastboot by powering the phone down. Then hold power and volume down until you are in the bootloader. Select fastboot and hook you phone upto your computer. You should see the phone say fastboot USB. You computer will install your phone. Then run the ruu file and follow the instructions.