This message you get when your computer does not send a video signal on to the monitor..If ti seams to start and the fan is working ..check the cables to be proper inserted (the vga cable ..the one with protection screws on ) ..and if all is in place than it may be the video card to blame ..
If you have a pci or agp card installed ..other than the on board video card ..use that ..cause if you plugged it in the on board card ..it will have no signal as long as the pci card is inserted..If the agp/pci one is not working ..and you do have a on-board card ..remove the one in the slot ..and use the on board one until you will get a new card
let me know what you have managed to do ..