It appears that the sound that is built into my Asus motherboard was originally C-Media (I think). But, at some point I installed another sound card (Diamond Multimedia) because the mic jack on the one built into the motherboard stopped working. So, I have since been using the sound card that I installed (Diamond) because I need the mic. But, somehow the Diamond sound card and it's drivers must have been working with the C-Media drivers that Windows 7 downloaded. I know that doesn't make any sense, but if I disable the C-Media drivers, the Diamond sound card and it's drivers stop working. I know for a fact that the sound was coming from the Diamond sound card because I have my speakers plugged into that card and the mic was working.
I have tried both uninstalling and disabling the C-Media drivers before reinstalling the Diamond Multimedia drivers, but it seems that the Diamond Multimedia Drivers will not install unless the C-Media drivers are installed first. It doesn't make any sense to me. I thought that the C-Media drivers were for the sound built into my motherboard, but now I'm not so sure. Because, like I said, when I disable the C-Media my sound stops working.
I don't know how to fix the error messages that you saw. In device manager it actually says "C-Media PCI audio device". I'm assuming that is my built in sound and not the Diamond Multimedia card I installed in a PCI slot, right? The only other one listed there is NVIDIA, and I would think that would be my NVIDIA graphics card. I just don't know why the one that says C-Media seems to control the Diamond Multimedia sound card. And why is there no mention of Diamond Multimedia in Device Manager?