After downloading the FMOD file from this site and installing it, ESF 1.2 worked fine. However, I have a mod called Sven-Coop, and when I try to play it, it gives me the same error I first got with ESF about not being able to open client.dll. To remedy this, i keep two versions of FMOD in My Documents, the one I downloaded for ESF and the one that came with Sven. If I want to play one mod, i copy the appropriate FMOD over to the half-life steam folder and play it. However, I dont want to keep copying FMOD's over every time I want to play a different mod. What else could I do?