When using 3 monitor everything works find But If I add a fourth monitor I get screen lag when I have all the applications running to do my day to day job. I also have issues where things will freeze and not disappear on my monitoring system. I am using a Dell OptiPlex 990 that have a 240 watt power supply with windows7 as the OS. The video card that I am using is a VisionTek 5570 1GB VHD PCIE Video card5570VHDCI1g. I cannot change the power supply to add a bigger video card any suggestions. The computer has 4 gigs of memory, I add 4 more gigs and no change.