Hello everyone -- one of the computers at work stopped working. It was fine one day and the next it turns up that the fan starts spinning, and nothing else happens. The monitor doesnt come alive. The fan keeps spinning and the light of power is on, but the computer screen does not come alive.
I've changed monitors, in case it is the monitor, but nothing
I've changed HDD, but nothing
Disconnected the fan, nothing

Anyone, please, any idea?

First try checking your PSU. If it is ok then your motherboard is dead.

Have a look here: Tutorial: No POST (Power On System Test)