wav sound problem. help

i recently posted a thread titled: Sound problems!!! Help i've had no sound for 8 months. this was sorted out but now i've noticed that the start up for windows. there are many others and it seems that all the sounds are .wav files.i went into control panel, sounds and audio devices and then sounds and played every sound in the list and none of them work. a message like this comes up when i try playing the startup tune: Windows cannot play the sound %systemroot%\media\windows XP startup.wav. your sound card may be in use.

can someone please help thank you!