The Sound Blaster Live! sound card that ships with Dell computers comes with a utility to quickly restore all the settings to the defaults. This will fix most problems that are encountered with this sound card. To restore to the original settings, please refer to the article below:

How do I restore the original settings for my Sound Blaster Live!? sound card?
http://support.dell.com/support/topics/global.aspx/support/kb/en/document?dn=1014911&l=en&langid=1&c=us&cs=&s=gen