Just thought about it, not sure if the 175.xx's will work with your GTX. Try them, but if it doesn't work, add the custom rez w/ ALL the settings in this picture (use manual to adjust the settings, ignore the "auto" in the screen shot- it's just so you can see the values). You will have to change the timing standard to "CVT reduced blank" to get your pixel clock and Horizonal Scan rates in the right neighborhood. From there, just switch it back to manual and fill in the other settings. Save and adjust your rez through windows or the nv panel, not the GXM. I have gateway 24" -inch'ers, so I'm sure our timings might differ, but try it anyway.