Have you tried a fresh clean install of Windows 10 to confirm no integrated audio device is found by Windows? Re: presuming that there is a pci slot.  Actually the motherboard has no PCI slot only three PCIex1 and one PCIex16.  You can try a $15 PCIex1 sound card like this one [IMAGE] [IMAGE]    
My Inspiron 620 has lost sound suddenly, and the sound card does not appear in device manager. All efforts to trooubleshoot/reinstall the Conextant (?) driver fail indicating a dead sound card.  My question is can I install a sound card and is there any type/brand/model that can be recommended to install into this desktop? I am presuming that there is a pci slot for it. Thank you for any advice.  
Inspiron 620 Sound Card options?