I can't enable SLI on a Windows XP 64 system having a Supermicro X7DWA-N motherboard with two Nvidia Quadro FX 1400 graphics cards. The Nvidia control panel does not show the SLI configuration tab. I used TechPowerUp GPU to verify that SLI is not enabled. I set the performance mode to single display but the SLI is still not enabled. I have the 176.04_quadro_winxp64_english_whq driver installed. How do I enable SLI?