1) Open Goldwave
2) Open sound file you want to save in mono using Goldwave
3) Save using goldaves
a) in the pop box, look under the Attributes section. The pull down window has many choices to choose from no matter what format you're using. Mono should be one of the choices under the Attributes pull down menu.
As of 23JUN13: I released a new small texture mod! Check it out here