sound playback slower then video

sound playback slower then video and as it gets closer to end of the film it gets even slower.
Imagine watching a 1.:30 mins movie.
it begins OK and i notice that gradually sound starts to play slower then video so in the middle of film characters open mouth, say a word then close the mouth and only after that i hear what they say.
Sound delays with every single avi file.
Sound card is X-FI creative with latest driver.
Fresh windows installation with nothing installed but the driver
No video codecs installed (i instaled them later to se if it helps but it doesnt)
i had this problems with earlier W7 RTM releases and with official W7 release as well

Can someone help me to understand what is going on ?
Sound card is not slow, its an ASIO card for music developers. Fast and very powerfull. I payed almost $200.00 last year and it has Windows 7 driver

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