Today I saw an article about a half-gig, 24000 square-pixel high-res composite image of the moon.

^{(This is a much smaller version of the image)}

I find astronomy interesting, so I thought I'd download it and take a look. With 4GB of RAM and an i5 processor, I figured my computer could handle it. Unfortunately, the built-in Windows Picture Viewer didn't do such a great job. While it opened the file without a problem, zooming in was ineffective. The zoomed out image loaded, but zooming in just showed a scaled-up version of the zoomed-out version, not any detail:

Closing the picture viewer also took a very long time, and the whole process used up much more RAM than the 500MB of the picture (usage went from 1.3GB to 3.8GB).

What other software would work better for this? I would prefer something that is free and fairly simple. I don't really want to use an editor (like photoshop or GIMP), just a nice lightweight viewer. Any suggestions?