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 free and lightweight configuration utility for Windows XP and Vista that allows you to edit program associations, icons, context menus and other properties of various file types displayed in Windows Explorer.
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.
Download types from here