go here
http://www.htc.com/us/support/touch-...int/downloads/
and under "software upgrade" there is a link "more", click on that. it tells you how to flash a rom. then download it and flash it.
basically, you install Microsoft Activesync (for xp) or Windows Mobile Device Center (for vista or 7), then all you do is connect the phone to the computer, choose activesync on the menu that pops up on the phone, then open the rom you downloaded. then click through the prompts.