Dual Monitors (same model) - Color Mismatch

Specs:

2 HP vs17 LCD Flatscreen Monitors
NVIDIA GeForce 6600
Windows XP


I've been using one monitor since February, it came with my comuter. The other arrived yesterday. Both monitors are set to the Factory settings, but the colors are severely mismatched. I've tried adjusting the Gamma, Brightness and Contrast settings on each monitor, resetting the default display in Bios - even messing with the advanced settings in the GeForce 6600...just will not match up.

Is this an issue with the graphics card, the monitors themselves??? Is there anything else I can try. I do web design, so it's important that the colors match between monitors. Am I wrong in thinking that two of the exact same monitors (both new, fairly), should be capable of displaying the same?

Any suggestions or advice are greatly appreciated.