NVIDIA Digital Flat Panel LCD driver options:
Here's what I've found. There are 4 options on how to handle images that are not at the monitors native resolution (in my case 1280x1024).
As many people know, 1280x1024 is not a 4:3 (1.33) ratio. In fact it's a 5:4 (1.25) ratio. 1280x960 would be 4:3. So, when scaling a game (or emulator such as epsxe)that is in a lower 4:3 ratio (ie, 640x480, 800x600), 2d items can have weird stretching effects (vertically, because 1280 is to scale but 1024 is not). Here are the 4 options when dealing with a lower resolution than native.
1) Display adapter scaling. The image is stretched to fill the whole screen but the video card is used to calculate the stretching.
2) Centered output. The image is left "as-is" in the center of the screen and black bars surround the image.
3) Monitor scaling. Same as "Display adapter scaling" except the monitor just stretches the image to fill the screen.
4) Fixed aspect ratio scaling. Display is stretched, but aspect ratio is kept intact. On a 1280x1024 monitor any 4:3 display (640x480, 800x600, etc) would be stretched to 1280x960 as this would fill up the screen width and leave small black bars at the top and bottom (64 lines total to be exact).
For epsxe, this leaves me with only two options. "Centered output" and "Fixed aspect ratio scaling." Since I've set epsxe to 1280x960, these modes will be identical for epsxe, and stretching will not happen. I will leave my monitor at "centered output" for games run at 1024x768 and higher since the interpolation that occurs looks so crappy in non-native resolutions and these resolutions are big enough that the image is still fairly large. If I ever have to use resolutions lower than this (ie 800x600, 640x480), I'll change to "fixed aspect ratio scaling" and live with the interpolation and tiny black bars.
Hope this post helps explain to a few others what I've learned.