Computer wont start up after being off for 2 weeks

I just got back from a 2 week vacation with my computer shut off and the power strip turned off and now my computer wont start up.

Now that im back i tryed to turn it on and ...

My keyboard and mouse stay black (they light up) and my screen stays completely black.

However the fans on my motherboard, video card and case all are running.

if i hold my harddrive i can hear and feel it running.

the cd roms drives open and close so i know i have power.

my power supply is acting very quiet with its fan not even moving most of the time.

I dont know if its my harddrive or power supply that went out and i dont know why (my computer has been completly turned off for 2 weeks)

So my question is which piece of the computer broke or how can i find out?

no i dont hear any beeps. I think it may be the Motherboard but i dont know how to check it if its broken or not.

thanks soooo much for telling me about the ram. i opened the computer up again to do what you said and take out the ram and i saw 1 stick of ram wasnt pushing in all the way.

i pushed it in and started it up and its works! thanx!