Don't talk to me about Windows Vista! Especially sound problems and Media Player.
I'm not sure about your specific problem, but another one in my box is that Media Player would play most of a track and, about 20 seconds from the end, crack up for a second or two, before continuing as normal. (There is a workaround for this one, so if anyone's having problems with it, continue the thread and I'll explain.)
Not much fun. Even worse, Media Player 11 will not rip CD audio. I reinstalled XP - on a separate HD - but then I got NO sound at all, even though the device manager said the codecs were fine.
How did I sort that one out? Simple, I switched to Linux on my second hard drive and that's where I do all my music management.(Storing files, burning CDs and the like)
I know this is a Vista thread (and I'm a Vista user) but I'm finding that Linux answers many questions that Windows can't.
By the way, on the Vista thing, OS updates are always dodgy - it's normally better to clean install with the full OS instead of an upgrade.
That's if you can afford a full Microsoft OS!
(BTW, what spec's the machine and what version of Vista are you using?