Have an off-brand PC (Systemax) that died after 18 months. Won't boot. PSU and other fans come on. Hard drive spins. DVD drive seems dead, won't open. Video posts "no signal." Nothing after that. No warning signs of problem.

Tried swapping in a different power supply. Same results.

What else should I try?

try taking the battery out of the motherboard for about 5 mins and put it back in and try to start the pc

Any beeps when you turn on the system?

Do you have a graphics card in the machine or integrated video?

If there is a discrete GPU, I suggest you try it on a different machine to see if it works.

same to my problem ..

my motherboard also won't beep. and have tried to unplug all peripherals to check if the motherboard still beeping .. but unfortunately it won't .. so it means it's ruined...

)

the 2 technicians said so ..

You know guys why my motherboard ruined? .

ans: I just cleaned the heat sink of the processor )

then the technician said , perhaps when I was cleaning it some particles have dropped to the motherboard and cause it to have a short circuit .. I think it's called "TINT" ?? just not sure about it ..



haha

You're talking about TIM, thermal interface material. But I don't think that the OP tried to clean his HSF. So that's not necessarily the issue.