PhotoView is a simple portable image viewer with one or two unusual extra features.
Browsing works much like most similar tools. Click a folder in the Explorer-type pane and you'll see thumbnails of all the images it contains; clicking one of these will display it in the preview pane.
The viewer is more thorough than most, though. Turn on the Magnifier (View > Magnifier), for example, and you'll get a resizable rectangle which you can drag over any part of the image to see a magnified view (far more convenient than always zooming in and scrolling, though you can do that as well).
There's also easy viewing of image EXIF data, and oddly the program makes it look as though you can edit this: you can put your own name in as the photographer, say. But for some reason any modification you make isn't saved.
A histogram gives you a quick look at the image colour balance, and you're able to apply a few basic manipulations and filters - flip, rotate, invert, greyscale, equalise - before saving the results in a variety of formats (BMP, GIF, TIF, JPG, PNG).
It's all fairly basic, but well presented, and perhaps the program's main selling point is its extreme portability: the authors say it should run on every version of Windows from 95 through to Windows Server 2008 R2.