XPS 8900, orange blinking power button?

Hello all,

I tried to install an additional optical drive (an LG blu-ray burner drive). After installation, when trying to start the machine, the power button keeps blinking orange and wont go past it. Power button starts with the white light and immediately turns orange and stays orange in blinking. I tried hard power off the power off button, it comes back automatically in a few seconds and back to orange blinking. Following tried so far with no luck

1) Verified all connections, memory cards, power connections to all devices etc.

2) Removed motherboard battery, power button pressed for 15 sec (power recycle), replaced the motherboard battery with a new CR2032 battery. Tried same again.

3) I could see all internal fans (CPU, powersupply, and tower fan) working fine

4) I could see the existing and new optical drives opening and closing without any issues

5) Tried restarting after connecting only one of the optical drives (tried both the original and the new separately)

6) Before shutting down (for making changes), there was message "shutdown after windows updates" and I selected that option for shutting down. I should have verified windows coming back before opening up, but didn't do, not sure whether anything to do with windows.

7) Now the power button only stays in orange blinking not even getting to BIOS.

Any help / guidance is appreciated. Seems motherboard is toast