Main Features:
- Add new file extensions.
- Associate a registred file extension with another program.
- Delete unused file extensions.
- Copy registred filetypes.
- Change the icon of registred file extensions.
- Change description of filetypes.
- myExtensions is absolutely free.
- Look & Feel from desktop Explorer (-> Registered filetypes).

SOURCE

http://www.badschwii.com/software_features.asp?swid=2

Reviews:

***** [Apr 25, 2009] by daddydave using Dell Axim X51v
Great, does exactly what it says! This is one of those "programs that Microsoft forgot." I installed it to see what app the .vce extension was associated with so I could remove all traces of Digital Movie List from my PDA. myExtensions is definitely worth keeping.

***** [Feb 25, 2005] by Richard using Toshiba e830w
Excellent. I lost some file associations when trialling and then uninstalling an application. Had them fixed in minutes.

***** [Nov 28, 2004] by HumbleOpinion using Dell Axim X50v
I had installed WinAmPAC to listen to .ogg files and the program associated itself with all audio file formats, including .wma and mp3. The program raised an error message that was unreadable, so I uninstalled it. The uninstall did not reassociate the audio formats back to Windows Media Player, so my files were left as orphans. My Extensions fixed the problem for me in no time.