Hi, I have recently bought a second hand E4024 desktop computer and it was full of dust (about half a centimeter thick in places). to do this i used a fine brush and compressed air. it seemed to go ok but when I reconnected it, it wouldnt boot up and the two fans are spinning. the green light is also on.
With dust that thick, just moving it could have loosened a connection. If you press down on the main heatsink cooling fan, is it stable on all four fixing points? Detach and refit all the connections to the motherboard, hard disk and optical disks as well as the points where the power and reset switches and LEDs join the board.