Is My Motherboard Dead?

My third computer just doesn’t open after whole day of using it.
Was happily using it the whole day with my regular workload, internet, MS Office and some webpage designing. So I rested for an hour then back again but to my surprise it doesn’t open.

• No beeping
• No display in the monitor
• CPU fan is working.

I opened the CPU box to check what is happening inside. Everything seems to be normal. So I tried to reseat the RAM then power on expecting to hear beeping to no avail. Then I removed all connection and cleaned everything inside the CPU box, I was actually expecting that dirt is causing loose connection but still no joy. I also tried replacing PSU with a working one but still no joy.

I’m now checking for motherboard replacement. Do you think it’s the culprit?
It has Windows XP on it with all windows drivers updated.

Thank guys!