I've had a couple of ECS nm70-m motherboards just die for no apparent reason (they are used in some inexpensive zoostorm PCs).

If you remove the memory they will beep as they POST, so I knew they weren't completely dead.

I managed to bring them back to life by:-

1. Installing a PCI-E video card.
2. Resetting the CMOS using the jumper.
3. Powering on and waiting about 10-20 minutes, the machine will finish POST and jump into setup (honestly!).
4. Reflash the bios from a bootable USB stick (created with the excellent Rufus) and using the latest BIOS from ECS's site.

Back to working. This happend to two boards, one after installing a video card, the other all by itself. This method fixed both.