Several things will cause your MB to not come up, the most common one I see is a missing 4 pin power supply connector but ASUS isn't as bad as Intel at leaving that part on the board when it is completely unnecessary for a board that only draws 18 Watts dripping wet (just a figure of speech, please do not wet your MB's), since this board supports both DDR2 and DDR3, I'd borrow the memory out of someones laptop to check for boot with only one slot populated, Memory is the #2 cause of startup failures... #3 make sure that the CMOS clear jumper isn't in the "RESET" position (I build computers for a living and I actually got an Intel board last week that had the CMOS jumper in the wrong position), you can find this in your motherboard manual... if all that fails then try checking the power switch for normally open/momentary closed operation. And if all else fails, try a different power supply (some older power supplies, particularily ones built between 2000 and 2005 had a minor capacitor glitch which caused some of the larger electrolytic capacitors to fail due to someone building them by the wrong (incomplete)formula , I have seen several power supplys that were shelved from that era simply fail when they were re-powered)
and lastly, there is potential for damage when the board has the heatpipe assembly mounted, I have actually cacked a tiny corner off of the silicone part of the processor chip (on a D945GCLF2, which, while it didn't immediately kill the board, it quickly overheats and kills itself within 5 minutes. (I have modified hundreds of boards with heatpipe assemblies, and this has only happened once to me, I much prefer the sealed packaging of the core 2 series processors, but Intels efforts to produce a low cost processor prohibits this type of packaging on the Atoms)