The other day Chris was telling me about an image preview tool that he uses called FastStone Image Viewer. It is free software that can either be installed or run as a standalone executable. You can use the software to view, resize, and touch up photos, as well as do things like make a slide show.
The software is by FastStone Soft. Their web site is very simple, and says the following:
We are developing graphics and photo programs to share our ideas with people, hoping that these tools will be useful to people worldwide.
Along with FastStone Image Viewer, there is also a screen capture program, a smaller image viewer, and a photo resizer tool.