If you are a WON user and trying to use Opposing Force Redux, you may run into some sound problems.
Redux uses 16 bit sounds for the most part and they are not supported by the WON version of Half-Life. We only support Steam installations of Half-Life for Redux, but you are not lost.
A forum member, Dornanu, has found a fix for all you lucky people. To read his findings, head to the forums under General Discussion or go to the Files section of the site to a link to his tutorial to how get the sounds working.
If WON users are running into other problems, this tutorial might fix more than sounds but thats what it has been tested for thus far.