Hi: A motherboard I have has four PCI sockets. Anything I plug into the first one or the third one makes the BIOS not even to beep when booting. With every other one empty,of course. How can it possibly be?

Bad motherboard?

Can you access bios when a card is in slot 0 or 1?

I've found the BIOS does not beep even with all slots empty. So, according to the generic BIOS beep code, the power source is faulty.

No BIOS beeps just means that booting has failed.

It could be the power supply, or it could be caused by other things.

BIOS has the capability of sensing CPU voltages, as you will be able to see by entering its menu. And in a sticky post in a hardware site, they list the BIOS beep codes for

(a) Award.
(b) IBM
(c) AMI
(d) Phoenix

Besides, a general table with the following header: "There are BIOS brands which have there own codes but mainly they are these" (a little vague statement). _This_ table gives the following for no sound: "Faulty power source". The other tables do not list the "no sound" case.

OK. Mine is an AMI mainboard. What am I supposed to think?

You've supposed to think, not just read. Dont take that the wrong way, computer electronics are complicated, but with a bit of thinking time things can become clearer.

If the motherboard is dead, its not going to beep is it? Thats just one thing that can stop the BIOS from giving you error code beeps. There is a long list of other possible causes.

I only sticked to the tables. Why thinking?

Because tables cant show you everything, even if they wanted to.