In Windows, each file has an extension in its filename which is used to identify which program will open the file, and which icon should be attached to that file. These can be changed fairly easily from within “folder options”, but the interface is not all that user friendly.
Types is a worthwhile replacement to the inbuilt Windows file type utility. It works on both Windows XP and Vista. It also offers a large display window so that you can easily find the extension you want tinker with.
To use Types, right click on the extension you want to edit and select properties. From the window that opens, you are able to change which program will open up the file, the extensions icon, and a few class options, but you shouldn’t need to worry about those.
This program does a small job well, and it is an improvement on the inbuilt Windows options.
Types is available for free from SourceForge.