My sound is working but there is no sound

Hey guys, sorry if this is in the wrong topic, I looked under tech support but there wasn't a category for sound, here goes!

I had my computer fixed about a month ago, and it is working great, the only thing is that the sound isn't working. This is what I cancelled out so far:

I tried plugging in different speakers or headphones

My drivers are up-to-date

Nothing is muted when I check my Playback Devices

Here is what I have as far as sound: Digital Audio (S/PDIF) that is what is checked and that's the only one available. But when I go to Control Panel/System/Device Manager this is what I have listed.

Sound, video and game controllers-
- High Definition Audio Device
- NVIDIA High Definition Audio ( x 4 ) there are four of those listed.

When I right click sound, video and game controllers and select scan for hardware changes my computer starts to say installing driver updates, and then it fails, this is what comes up and I have no idea if it relates to my problem.

There is a yellow button "!" next to Coprocessor under Other Devices, and it says "Device driver software was not successfully installed" No driver found for coprocessor.

Then under Coprocessor Properties it says "The drivers for this device are not installed. (Code 28)"

A little background on my computer- it was broken with a nasty blue screen and my friend fixed it for me, I had to have the motherboard replaced. He threw in some other stuff too but may have messed with the sound I'm not sure. Here is my system:

Rating: 3.9 Windows Experience Index
Processor: Intel(R) Pentium(R) Dual CPU E2220 @ 2.40 GHz
RAM: 4.00 GB
System Type: 64-bit Operating System

Sorry if all the information isn't there, I'm not that much of a computer guide but I've been at this for a while trying to fix it. Any help would be greatly appreciated thank you in advanced!

Anthony

Edit- I forgot to mention that when there is sound going on, the volume panel is indicating that it is working but nothing comes out.
 
I have a few questions.

Are you using a onboard sound card?
Are you using a optical cord from you pc to your speakers, or standard copper?
What types of speakers/receiver are you using?
What windows are you using?
What motherboard are you using?


Screens shots would be helpful.

Cheers
 
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