There are two things you can do to make these pictures look their best.

The first is to set your color depth to at least 16, and preferably 24, bits. If your color depth is set to 8 bits, your monitor can only show 256 colors. This isn't enough for photographic images, unless they're nearly monochromatic.

If you're running Windows 95, 98, ME, 2000, or Windows NT 4.0, right-click on the desktop, and select "Properties." Click on the tab called "Settings." Look at the section labeled "Color Palette." The pull-down menu will have entries for 256-color (8-bit color), 32000 color(15-bit color), 65000-color (16-bit color), 16.7 million color (24-bit color), or something called "True color." The greater color depth you pick, the more memory your display adapter needs. When it starts running out of memory, it will restrict the resolution that it allows you. Play with the resolution and color palette settings until you reach a compromise that's comfortable. If you have 2MB of display memory, you should be able to get to 600x800 at 24-bit (24-bit or "true") color, or to 1152x862 at 16-bit color. 16-bit color looks pretty darned good, so that's what I'd pick if I had a 17 inch monitor, to get the extra resolution. If you have a 15 inch monitor, try 768x1024 at 16-bit color, or 800x600 at 24-bit color. If you have 4 MB of display memory, you don't have to make these tradeoffs, and you can go up to 1280x1024 with 24-bit color.

If you're running on a Mac there's a monitor control somewhere, probably in the System or Control folder. If you're running Windows 3.1, the display adapter control panel is in with the others.

Got your color depth set right? The next thing is to adjust your gamma.