The first thing would be to check for any conflicts in the device manager...Start>Run> type "devmgmt.msc" (without the quotes)>Enter...Click on the view tab and select "show hidden devices"...Click on the "+" sign for sound, video and game controllers...Check for any Red "X's" or Yellow "!'s or "?'s"....Also click on the "+" sign for system devices and look for the same things.
If you find that there are conflicts with your sound card drivers you have some options...You can update, roll back, or un-install (re-boot the computer and let windows find it). You can also choose to download the original drivers from Dell using the following link. Just make sure to indicate what operating system in the drop down box (XP or Vista)...When the page loads look for your sound drivers in the Audio section.http://support.dell.com/support/downloads/...tid=&impid=
If by chance you find conflicts in the system devices section, post them in your next reply and we'll go from there.