When you have just installed Microsoft Windows XP Service Pack 3 into Toshiba Satellite Notebook and your audio not working, you may follow this simple step.

a. You have to change CSDVersion registry key.
Go to "Start"-"Run" and type "regedit" and then click "OK"
Select plus signs on "HKEY_LOCAL_MACHINE" -> plus sign on "SYSTEM" -"Current Control Set" -"Control" - choose "Windows", on the right panel, select "CSDVersion" and right mouse clic k for "Modify". You may find the value is "300" CHANGE IT TO "200".
directly: HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\CONTROL\WINDOWS\CSDVersion

b. Reboot your Toshiba notebooks
c. You have to installing this HD Audio Hotfix "download from here"
d. Follow (A) method again to change CSDVersion key value from “200″ to “300″.
e. Reboot your laptop

I hope this method will fix your problem.