The links below may help you in determining what a specific
file type is used for, and what program to use to open it.
File-Extensions.org
http://File-Extensions.org/
Filex File Extension List
http://camalott.com/~rebma/filex.html
The Programmer's File Format Collection
http://www.wotsit.org/
Understanding MS Windows File Associations
http://www.microsoft.com/TechNet/prodtechnol/win98/maintain/assoc.asp
What Is...every file format in the world
http://www.ace.net.nz/tech/TechFileFormat.html
TechTarget's What is every file format in the world
http://whatis.techtarget.com/fileFormatA/0,289933,sid9,00.html