file extension will not associate with a program

[Guest Nathan]

I'm trying to set up a file extension to be associated with a software

program on my machine. When I go into Folder Options, the program's file

extension is not listed. I add it. When I try to associate it with the

right software, it does not recognize it, even though I am drilling down in

my programs folder to the exe file for the program. The software I'm trying

to use is not even listed in the Programs list even though it is on the

computer (and I can open it). Why is this doing this?