Some time ago I lost sound on my Toshiba laptop (I'm not sure exactly when as the output was going to speakers that I only turn on when listening to music etc.). The Device Manager is showing all "Sound video and game controllers" as missing drivers (Code 39).

Laptop details are Satellite Pro A series, short model number PSAACE. Operating system XP Professional with SP3.

I went onto the Toshiba site and downloaded the only audio driver offered for my model. This failed to fix the problem and I've now found that the Windows Update log is showing that some parts of the driver update are not happening (both on start up and when I reinstalled the downloaded package). Messages are of the form:

"Download ... is "PerUpdate" regulated and can NOT download"

There are also two crypt32 errors in the Event Viewer at the time of my attempted reinstall that look like the authentication certificate might have expired for some components. Message text is:

Failed extract of third-party root list from auto update cab at: <> with error: A required certificate is not within its validity period when verifying against the current system clock or the timestamp in the signed file.

I then downloaded the generic Realtek High Definition Audio package version 2.71 from the Realtek site, but the installer reports "no driver supported in this driver package". The messages in the update log seem to indicate the same failure.

Is there any way I can get working drivers to restore sound?

Grateful for any assistance or new lines of enquiry.