Computer starts up at a black screen?

Hello,
When i turn on my computer, it just goes to a black screen, no sign of the bio's screen or windows xp screen. No flickering or anything, no indication its connected except for the fact when i unplug the monitor the screen saying there is no cable on the monitor shows up. i tried a different monitor on it, same thing happens. It is connected to the on-board graphics card. I tried removing the hard drive to see if that was the problem, no luck. Shouldn't it at least show the bios screen? I tried removing the battery without any luck hoping it would reset any bios, I tried removing the ram, no luck. Any ideas on what is wrong with it?
System Specs:
HP Pavilion a804n
Intel Celeron D Processor 335 (2.8GHz)
512mb pc 2700 DDR SDRAM
80GB Hard Drive IDE
CD-RW Drive
DVD-ROM Drive
Intel Exteeme Integrated Graphics 64mb

Any help would be greatly appreciated. Thanks!

 

I even tried connecting it to my PCI graphics card, and no luck, same black screen