In cases like this the general procedure is to break the system down to only the components needed for POST. One of the things I like to also do is just remove all the RAM and see if you get the proper "no RAM" error tones. If you don't get even that much, then you either have a bad motherboard, didn't connect the PC speaker, or have a bad CPU.

If you get the proper error tone, then you add things back ONE AT A TIME, and test before adding anything else. So you might add ONE stick of RAM and see if the unit will give you the POST beeps. If it does, shut it off and add another stick of RAM, then test for POST beeps. Rinse and repeat with additional components until either the unit works or you find the point at which it's failing.