sound is mono

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I have an old asus A7V333 with on board sound chip(C-media).I was using Creative Audity for 4 years on it without problem.After making walkman in to creative we lost one channel(left channel).I supposed to lost creative sound card and than I deinstalled the card and try to reinstall software but said that "there is no audity card on system" than I took it out and enabled C-media on board sound card.It was mono too.I've installed the a new creative sound card but it was mono too.I loaded the bios features to default,I used the different operating system again no change.What can be the problem?

 

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I checked sound with headphones,2 speakers system.I am increasing-decreasing volume of left channel no effect on sound.Tonight I will check sound card on my old pentium 100mhz system.

Is there any virus eating left channels?