A\V problem Genius who solves this. details inside.Help!!!

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Hello
My problem is as follows: i have reinstalled winxp(Home Edition), i formatted my c partition and installed windows, afterwards i installed all updates(from microsoft) and all codecs(divx xvid even codecs packs).
Since then every movie i play no matter what player, there is a gap between the audio and video. The movie files are just fine they don't have a sync problem. The problem is not with codecs because it doesn't play well mpeg file and DVD movies.
Furthermore, it seems to me that even in windows itself there is a problem, for example in error message i see the box and afterwards hear the beep.
Before the reinstallation there were no problems, i tried reinstalling again(it's the third time) and nothing.
There are no hardware problems since i haven't change anything, and i tried different sound and video card and i still have the problem.
Please help me. any suggestions will be highly appreciated.
Thanks in advance.

My specs
intel Motherboard D865PERL
nvidia Geforce4 128 DDR
Memory 256 DDR 400Mhz
Onboard soundcard SoundMax