I'd be very surprised if a stock Dell machine's sound card is not supported natively by the kernel
(doubly surprised if it's onboard sound)

Chipsets for sound devices are all standard
and Intel's High Definition Audio is most definitely supported
but it's possible you may have some exotic sound chip that doesn't follow intel's reference design

are these the instructions you're following?
https://help.ubuntu.com/community/HdaIntelSoundHowto