XnView is a program that will help you to read any graphic files to over than than 500 different formats and then convert them to other formats such as GIF, BMP, JPG, PNG, multi page TIFF.

This program also able to display video formats, many digital camera formats and more exotic formats such as Amiga IFF and Calamus.
The Image viewer (Browser) is similar to Windows Explorer. You simply navigate the directory structure as desired and any image files found in a directory are displayed in miniature (Thumbnails). This lets you keep an overview of the images available at the same time as letting you quickly view and select specific images.