What model Dell is it? I can check the downloads, but if it'a a 2006 dated driver
then it's not for Win 7 and probably not for Vista either and you need Vista drivers
, at a minimum.
Stuttering on Dell's is generally the wrong drivers. On older XP systems (PC's that came with XP) if users used non-Dell drivers that would happen.
Some drivers come with a "Sonnd Enhancement" panel that you can set echo, reverb, chorus, etc. If you have that and have any of those enabled that can cause what you are hearing.
Finally, many users on the Dell forum with older PC's that do not have Dell support (at least for Vista) have resorted to installing a separate PCI sound card (on Desktop systems) to remedy sound issues.