I use XP, GeForce, & 2 LCD Monitors. I experience no display problems with P4, PPro, or P5 at all. "input not supported"? - I'd make sure the drivers were installed for my monitor, then check to make sure the Monitor cable is securely fastened at both ends, or swap it out entirely. I've seen cables where the pins lose contact after a while due to heat/expansion. Except for a thermal-related Graphics adapter failure (wouldn't hurt to make sure the card is securely seated in it's slot), an intermittent cable is the likeliest cause of such an error message that I've seen.