problem with sound output
dear fritter's!
i hope someone can help me out... even if my problem is regarding a pc with windows xp 
currently i'm experiencing the following problem: i start up the pc, play videos or sounds with windows media player, ok. works fine... but everytime i start up winamp and try to play an mp3 file with it, i don't hear anything from the sound output. even if i switch the output plugin to my second sound card, nothing. i'm a bit frustrated at the moment, i already tried to reinstall the hardware drivers and double checked if it's just a volume setting somewhere, didn't help at all.
the interesting thing is, after i shutdown and turn on the machine again, it works. as long as i dont open winamp and try to play something. 
i don't want to reinstall, as i need the pc on saturday for dejaying (virtual dj).
any suggestions?
specs:
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acer rc900
pentium 4 ht 3ghz
2gb ram
acer mainboard with integrated realtek soundchip, second card is sound blaster pci 512
xp home sp2 with latest updates

