[TooCoolForSchool]

I installed the soundblaster AE-5 Plus soundcard into my desktop PC, and now all dialogue in video games is completely mute.

Why is this, and how do I fix it?

[Xen]

Check you sound card drivers are installed and check your windows sound settings and make sure the application is using the correct audio device.

[.eXe]

The default sound device is probably configured to be the wrong one. You'll need to go in to Windows sound settings and double check what your default device and default communication device are.