MediaInfo - this is a great utility that integrates with Windows Explorer allowing you to read meta data on any files such as frame rate, dimensions, etc.
GSpot: A great little utility. It lets you scan the 4CC (Character Code) information for an avi file. It will then tell you what codec that avi file needs to play, and if it will play on your system.
VLC Player: A very nice open-source, cross platform player that plays a number of different video file formats.
File Renamer: This is a great file renaming application. There is a basic and a premium version, the basic version should be free to try. This is perfect for scenarios where you might have a series of images output from a program that are not sequentially numbered. This application allows you to rename those files so that they are in a numerical sequence.