sound problems with a dell latitude laptop. HELP !!!!!

hi all,
ive got a dell latitude laptop ive had it for about a year and the i always use to listen to music on it, then all of a sudden the sound just stoped working. i dont know why this had happened and i dont know how to solve this problem.
when i go to play a music track i get a message saying-
"can not open the audio device. Another application may be using it".

I Verifyed that no other programs are using the sound card by

1. On the Windows taskbar, click the Start button, and then click Run.
2. Type taskmgr in the dialog box, and then click OK.
3. Click the Applications tab.
4. Click each program to highlight it, and then click End Task.
5. Attempt to replay the content

but that didnt work. so i tried to check for incorrect or missing sound card drivers, by (Start > Control Panel > System) then Clicked the Hardware tab, and then the Device Manager button, once i opened it i noticed that it was totally empty. i dont know if it should be like that or its missing. could somebody please help me out and tell me what i should do or how to get the sound back on the laptop.

thanks
mubs.