P5V800 automatically powers on but can't boot, no display

I have a P5V800 box that automatically powers on when I turn on the ATX power switch. The green LED and CPU fan were always on, but won't boot, and no displays at all on the monitor. The machine was working before till I removed the button battery on the motherboard. Any advice on how to fix this are bery much appreciated!
 
"The machine was working before till I removed the button battery on the motherboard"...
Why did you remove the CMOS battery in the first place? By doing this, you cleared the data that the computer needs to be able to start up. Did you replace the battery?
 
I was probably looking for a battery for another machine. So I took out the battery as I didn't use the machine for a long while. I didn't replace it and just left the machine for about 3 years till now as I am thinking to use for a project but it's not working now..

Was it the case that the BIOS was gone since I took out the battery and didn't replace it?

Thanks,
 
If you installed another button battery (CMOS battery) and you still can't even see the boot or bios screen, the motherboard is toast
 
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