Assox

The Assox application was designed to be a versatile tool for manipulating Windows file associations.
Its primary aim is to create file type associations quickly and easily from a configuration file. It also lets you create shortcuts, startup items, send-to items, folders, start menu items, and more. You can associate programs to handle your e-mail and Internet calls. You can run programs and use several user-contributed add-ons to extend functionality.
Assox writes into the Windows registry. So what is different from other similar utilities?
The difference is that Assox knows how to cleanly remove what it writes into the registry.
So, at any moment, undoing all changes is just one click away, and you dont have to figure it out.
Assox supports relative paths, so you can use it with your portable programs on a USB key. It also includes many features that help to manage a multi-user Windows installation on a fixed hard disk. Assox supports a command-line, silent batch mode for experts users, and an uncluttered graphical view for first time, less-experienced users.