no beeps , not booting up

Hey Guys anyone tell me what to do about a computer that wont
boot up. Has power to the mobo, to the cd, floppy, processor
fan, and other peripherals.
It is an ASUS mobo p4t-e 1.6 ghz processor
512 meg rimm in pairs
new HD that works
I get no errors just not starting up. no botup screen no beeps.

Any suggestions?