windows media player 10 no sound

hi I just recently upgraded my WMP9 to WMP10
after installation all sound on computer stops working
never had this problem before on my old computer
The sound works fine now after a system restore but
im just wondering if anybody knows what the problem can be

AMD athlon 64 3500+
2x512mb ocz dual channel
geforce 6600gt
msi k8n neo4 platinum sli
36gb raptor

WinXP sp2