|Right-click My Computer, Properties, Advanced, Device Manager.|
Sounds like the sound card is no longer installed. If it's listed in the Device manager showing a conflict, remove it and reboot the computer. If that doesn't work, you'll have to add a hardware device, and then install the drivers for the card that's installed.
You should have gotten a Dell Resource CD with your computer. The drivers would be on that.
"So won’t you give this man his wings
What a shame
To have to beg you to see
We’re not all the same
What a shame" - Shinedown