Do I have a dead motherboard? No beep, no BIOS screen.

you may have a dead power power supply. but i would first plug a lamp in where you plug your pc in to see if the outlet still good. if you have a power stip plug the lamp into it to see that the power strip works..power stips do have a reset button or fuse that can trip. if there fine i would check to see that someone not playing a joke on you and move the voltage switch on your ps. most ps are made for 120 and 240v and have an orange switch to set them at 120 or 240.if the switch is set to your country voltage. I would then open the side pannel with the pc on it side and try turning the pc on. if the ps is working or trying you should see the fan or led blink or twitch..it not to say that ps is good but you need power to post a mb. if there no fan or drive spin up i would see if someone has a ps you can use to test.

If the pc is getting power (check to see if fans spin up or listen for the harddrive if its loud enough) try removing cpu/memory/graphcis card/any other hardware connected, with out a cpu or memory the pc should produce beep codes trying to POST (assuming you have a pc speaker connected to the motherboard).
if there is no beep codes with no other hardware connected good chance the motherboard is dead, before that though try a different power supply to make sure thats not the fault.

If there is no power getting to the pc try with a different power supply (borrow from a friend if you can, or buy a new one if you have to) and then apply the procedure above if pc still doesnt boot.

Removing the CPU will kill any possible beep codes.

First thing, system specs - including brand and model of PSU?

Then a quick check: unplug everything from the motherboard except CPU and heatsink, PSU, case speaker (if you do not have one, you really need one), and the case wiring.

Try to turn the system on. Silence indicates a problem with the PSU, motherboard, or CPU in that order.

If you do not have any motherboard LED's on, your problem is likely to be the PSU.

After that, work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.