Check to see if the mute button is checked in the MAIN volume control. Make sure he/she has their speakers all plugged in to the right audio output jack on the back of the soundcard. SOUNDBLASTER(tipically come with dell's) So the soundcard audio output should be the green hole.
Download Aida32 (It will tell you if the soundcard works)
http://www.webattack.com/get/aida32.html

AIDA32 is system information and benchmarking tool with full hardware & software information on 80 pages. It comes with a built-in hardware database and physical information for CPU, motherboard, hard disks, optical drives, chipset and much more. It can display the information on-screen