Boot Problems

[tbcomputer]

My Stats
DFI MotherBoard AD77 Infinity
512 PC 2700 Samsung
GF4 ti4800 Gainward 8X AGP
Athlon 2100XP+ w/ ThermalTake Volcano 9
400 Watt power supply

OK, Heres my problem.. about 1 in ten times can I get my computer to boot successfully. When I hit the power button everything fires up, just not the BIOS, POST, Ect. Now I have tried two motherboards, two power supplys, two video cards, three kinds of memory, two monitors, I have done just about everything. I cant figure it out. Any comments would be appreciated.

 

[BuckeyeComputers]

Faulty switch? bad grounding in the case? try it outside of the case and see if it does the same

 

[tbcomputer]

Thank you BuckEyE for your response

I have thought of this, since it is the only thing left to troubleshoot . I have seen a faulty case ground render everything useless in a computer before. I have had this Antec 1040 case for about two years now.. Me personally I am betting on the power switch, but I will try both troubleshooting recommendations. Once again thank you..
TPinky