I've not read the whole thread in detail, but didn't see if this has been checked specifically - have you confirmed if the Intel audio driver is actually installed?
It should look like the below image in your device manager.
If it's got a Q45 chipset then it's pretty old - what actually is the computer? Is it a brand name machine?
What do you see in the audio area in MSINFO32? The below image is from a 2nd gen Dell laptop to give you an idea.