Computer will not start up

[waterhouse]

When i start up my computer the fans turn on and the LEDs light up and i hear a beep then a pause then another beep. Then the computer shuts off. The parts are all new. I can't seem to find what is causing the problem.
specs:

ASUS M478T-E, AMD Phenom II X3 720 BE, 4 2gb ddr3 sticks of ram, using the on board graphics card.
Any help would be much appreciated

 

[batuchka]

Clear CMOS by moving jumper, remove mobo battery if u have to , wait 5 mins and try to bo basic POST test with just the single stick of RAM

 

[shaw24]

Did you plug in the 4 or 8 pin power connector next to the CPU?

 

[shaw24]

Read this as well: http://www.tomshardware.com/forum/261145-31-read-posting-boot-video-problems

 

[Onus]

Is the heatsink properly seated?

 

[prelude2250]

I would remove the mobo from the case. start with the essentials, i.e. cpu, ram, mobo, power supply. then see if the problem continues. if it doesn't then slowly start adding components until you get the same problem. If it runs perfect until you get it in the case then look for misplaced stand-offs or any other potential contact problems.

 

[waterhouse]

Best answer selected by waterhouse.