Go to http://www.support.dell.com click on Drivers&Downloads then enter the info to your computer then click the plus sign next to the word audio and then download the first driver you see or just click this link

http://support.dell.com/support/downloads/download.aspx?c=us&l=en&s=gen&releaseid=R94481&SystemID=DIM_PNT_P4_CEL_2400&servicetag=&os=WW1&osl=en&deviceid=2430&devlib=0&typecnt=0&vercnt=4&catid=-1&impid=-1&formatcnt=1&libid=3&fileid=122481