You may be able to get at least the basic sound working with the Realtek chipset drivers. Available for download from
here. You will need to accept their disclaimer and select from the menu on the left to access the drivers. I would suggest trying the generic AC97 drivers on offer there. As you already found out Toshiba is useless for XP drivers (because the machine was built and designed for Vista).
As and aside - why do you want to ditch Vista? The specs of the machine are ideal for running Vista.
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Cheers.... Kev
"The Definition of an Upgrade: Take old bugs out, put new ones in."
Please don't send me PM's for support. Post in the forums for everyone to benefit.