You have given too little information, that it seem impossible to determine where the problem is. How many beeps do you get when you try to start the PC? Afterwards, are you able to load at least the initial start screen or the PC shuts down completely?
I need to know if something has happened prior to the error that you get.
Please, come back to the topic to provide more details regarding the situation and give information regarding the configuration that you have. If you have performed some troubleshooting steps already, please mention them too.