I use iTunes
Apple - iTunes - Download iTunes
WinAmp's very good as well
Download Winamp Media Player 5.35 - Upgrade to Pro for Premium Features
Was there some update for WMP within the last couple of weeks? Maybe a M$ update that effected WMP? I don't like WMP but if you do, you could check out whether an update was recently released. I'm not a Vista user so I don't know whether earlier versions of WMP are compatible with Vista!