i ran some windows upgrades yesterday and lost my sound.i have a xps 410 with vista ultamate.it has internal sound which is enabled.i have the most currant drivers.when i check it in device manager it says its working properly and if i try to update the drivers it says they are current.if i open the speaker it says no audio devices installed.i spent 4-5 hours online with a dell tech who was unable to resolve the problem.what should i do?just buy a new sound blaster?will it even work?the internal device is a sigma tel high def audio codec.i really hope someone can help.  thanks