Ok with the Fusion webcam your suppose to have a full duplex sound card this is actually recommended on the box I am not positive you have that with the onboard sound now. A full-duplex sound card can record and play back sounds at the same time, if you can't thats possibly your problem.
Just installed a Logitech Fusion Webcam in a Sony Vaio RB30. After the install, I'm getting a crackeling sound out of the speaker with anything that produces volumn (like Movies, music and games). Using intergrate sound from the MB, 5.1, with a pair of 2.1 speakers. Tried un/reinstall web cam and updated software from Logitech. Any suggeestions?????
System
Sony Vaio RB30 3.0 ghz
512MB RAM
Radeon X300SE Vid Card

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