Hello and welcome to JustAnswer, I look forward to assisting you today. You should be able to go into the BIOS and disable the on board sound. That would give priority to your add on sound card.
Please let me know if you need further assistance.
To access the BIOS, restart the computer and watch the screen. You will see a menu flash to press the F2 key to enter the BIOS setup screen. Disable the on board audio first and save the settings then power off the computer and install the audio card.
My apologies for the delay. Can you tell me the BIOS version you have please?
Try looking under the Advance tab in the BIOS and check to see if the audio setting is located there. It may be listed as Onboard Device Configuration.
Were you able to locate the Onboard Device Configuration in the BIOS?
That is unusual even for Dell? When you access the BIOS, is there also an option for System Setup you can select on the same screen?
Do you have the manual for your computer?
Check the attachments to see if your motherboard matches please? If so, look at the audio connector on the diagram #16 to see if anything is connected to it.