I'm going to ask that you please use lower-case letters, it's easier to read than ALL CAPITALS 😉
Now, get your manual for your ECS board and look at page 7. You have DDR memory, so make sure that jumper JP1 DRAM Voltage (VCC) is set for 2.5 volts. While we're on page 7, make sure both JP1A and JP1B are set to 100MHz so your Celeron runs at its intended 4x100 bus speed.
Next, go to page 8. See the J2A/B/C/D and J3A/B/C/D jumpers? Make sure they're all capped, because you've got DDR memory, not SDR memory.
Now double-check that your CPU fan does in fact spin when the system runs, and double-check that the heatsink is firmly latched down so it's in good contact with your CPU.
Because you have an add-in sound card, it would probably be smart to disable the onboard AC'97 audio (see page 32 of the manual). Also disable onboard MIDI and Gameport.
Since the board has onboard LAN, either disable that or use it (I'd recommend using it).
ECS isn't telling what the specific IRQ-sharing situation is on the different PCI slots, but generally you should avoid using the slot next to the AGP slot, and possibly the one furthest away from the AGP slot, because those two often share their IRQ with the AGP port. So try just your sound card in one of the middle PCI slots and leave the NIC out as a test scenario, and see what happens now.
Good luck! 🙂