I have known about this issue for a while and as of yet I haven’t found a good solution (though, admittedly, I am yet to look for one!) and the reason as to why I’m posting this now is that I know I’m not alone in having this problem — I got two 
hits from someone searching “no sound macbook pro vista ultimate 2008”
The problem occurs randomly, but I’m pretty sure that I see it more after my MacBook Pro has resumed from sleep in Vista (Ultimate 64 bit).
The problem is that no sound will play out of the speakers even though the system is unmuted and should be playing sounds!
The only way I have found to get around this is to insert some headphones/speakers into the headphone jack and then remove them. This always restores the sound for me….. But, I will get on to finding out if there is a better solution than this and I’ll update this post if I find anything.
Does this work for you? Or have you found some other way to restore sound? If you have found another way, please comment.
Josh Anderson's Blog 
i just dual booted vista home premium on my 2009 MBP. Everything worked fine but I noticed the sound would distort like its gargling every 30-60 seconds. I tried repairing the driver but then I had no sound at all! So, I went to manage devices then uninstalled it. Then I did a fresh install of the driver. When it restarted and loaded the driver the sound worked again.
But, I still don’t know how to solve the gargling thing.
I’ve never had this problem or heard of it before so I don’t know what to suggest…. Perhaps look for a different driver on the Realtek site — I believe they make the sound card in most MBP’s but can’t comment for the new one’s as I don’t have one 😦
Does the same gargling issue happen when you have speakers/earphones plugged in? If it does then it’s probably entirely a (weird) driver issue. But if not then…. I dunno…. a firmware issue?
x64 Windows is supported by Apple now so you have a [slim] chance of them being able to help with this. I’d also post on the Apple support forums, if you haven’t already.
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