No signal

It means that the screens works properly, but it doesn't receive any data from the central unit.
1-Check if the VGA cable (blue) is correctly plugged
2-Can you hear fans make noise when you turn on the PC ?
3-When the PC is booting, can you see the Hard-disk LED waver ? L'urgent est fait, l'impossible est en cours,
Pour les miracles, pr�voir un d�lai ...