Yes well vista magically makes soundcards stop working.
The only problems would be vista and a soundcard not working to begin with, if it just stopped one day, it's almost certainly a hardware issue.
Check your mixer though, to make sure that your sound isn't actually muted, secretly
Your mixer can be obtained by right clicking on sound icon > mixer.
Of course, that's probably not the case.
Did you try moving the card to a different pci slot? That has solved the issue with some hardware with me in the past. Dunno why it fixed it, perhaps irq things or witches or something.
Vista may also have been set to use the digital out instead of analog out (or vice versa) check your settings from the control panel.
Hurray for teh logd!