normaly no output on the screen relates to two things
your CPU
your graphics card.
check that these are both inserted correctly. just take them both out and insert/ reseat them again. and follwoing from the Administrator's point, yes look out for beeps. try connecting the little pins on the motherboard to allow u to hear out for sounds. these can be crucial as they can direct u towards the problem.
you should at least get a BIOS on the screen or some sort of output once u get this you are sorted for life
good luck matey