Make P II up

we have a P II which was working fine resently but at present it is not giving display,we had changed the smps still the display is not there we have 5 to 6 Pentiums on the desk connected to a single 2 kva cvt,if the monitor of the same P II is changed & connedted to other Pentium It works fine, if the all m/c’s are off then the conserned P II works fine with its own Monitor but if another m/c Is made on the display Of the concerned m/c goes off emidiately & its smps work ie.fan rotates.
please help me out of this situation.