Nothing starts after pressing power button, not even the bios beep

[catax]

This is what happened to my friends comp a while ago.
He built his own PC and it worked fine for a 6 months, then his computer had random shutdowns. He replaced a SATA hard drive along with a new power supply, it worked for 2 months and started having the same random shutdowns. He stopped using it as frequent. A few weeks ago he tried to restart his comp it turns off after going into windows loading screen. i replaced the bios battery and reset the bios and now nothing loads. the power would be on and all the fans spinning and that's it. i took off his graphic card and tried using the on-board video card and still doesn't work. Any idea what's going on guys?

 

[sPlAtOiD]

Try unplugging everything and reset them. Pay close attention to the CPU that it is seated right and you have thermal paste on it. If still no luck try just one ram stick at a time if you have more that one in the system. If still no luck,Try taking everything out of the case and lay it on a antistatic bag leave your ram CPU floppy and hard drive and video card on the board and see which pins are the power switch pins and jump them to start the computer. What are the specs of this computer.

 

[catax]

CPU: Intel P4
Motherboard: ASUS P5LD2-VM
Memory: 2x 1Gig Corsair ddr2
PSU: ThermatakeX 480-550W
those are the things that are plugged in right now, and still not loading anything, just powered on.