Shoutbox

You might want to have this script, though it might not help with the sound problem, but visually you can still see whether the contact is still chating with you while having tab function enabled.
I'm not sure whether this script will work fine in Windows Vista RTM. I tested with RC2 and it works, so far no problem found yet.

This is the script created by TazDevil:
Messenger Plus! Live Enhancer

Hope this will help you.