You could try media player classic. Its will just about play anything audio or video and its really lightweight. Its very basic to look at but is pretty configurable if you start looking through its options. Its my media player of choice for quickly playing stuff (its ideal for auditioning load of samples due to the speed) and its free. Here the linky;-
Media Player Classic 6.4.9.1
If your after bigger and more fancier media player id recommend
media monkey. Ive been well impressed with this media player and its allowed me to dump that piece of shit known as itunes. Its free, will play any audio format, has some excellent plug ins, and sets your media collection up well from the outset. Its also good with big collections as well and will also sync with an ipod if you need it to. Ive been recommending this media player to all my friends since i found out about it a couple of months back. Its a cracking player.