What do you mean by it boots but no display. Having a display is a required part of a successful boot. How many beeps are you getting? Have you checked the basics. RAM, pull one stick at a time and make sure they are in the correctly oriented slots for the number of modules as per the manual. It matters where you put the RAM. Pull one stick at a time to see if you have a bad stick. Just because you have power to the fans and lights does not mean it has booted.