Computer won't boot, only shows motherboard logo

Hello,
my computer won't start, it only gets to motherboard logo (where i can press del to enter bios) and if i try to enter bios it stops aswell after "initializing usb controllers .. done
2040 mb ok ".
this happend after i had let it by it self for about a hour and when i got back my screen was black and i thought it was in hibernation so i tried to press a keyboard key and move the mouse after that didn't work i pressed the power buttom and it turn it self off. when i tried to restart it the screen was just black and it would not boot, then i reattached the ram to see if the ram was the problem and now i got to the motherboard logo, but not further except for when i press del and got to bios setup that stoped at "initializing usb controllers .. done 2040 mb ok ".
i have check the cables to the hardrive,dvd player and reseted the bios settings by removing and reattach the bios battery
would be where nice if anyone could help me with this, and srry if there is alot of english mistakes it's not my 1st languege

and if this is not the right place to post this problem please tell me where to so i dont bother others with it

edit: tried to press crtl+alt+delete and suddenly it started to work

Do you have any USB devices plugged in? I had an old computer way back when that would not POST if I left my usb card reader or a thumb drive plugged in.

I also had a similar problem with a USB device. Couple of weeks ago, I racked my brain trying to figure out the problem. Ended up being a bad printer that when plugged in, would cause the computer to freeze at the dell logo screen.