Some audio noise, such as static can be caused by Video and or video drivers
. You should have plenty of memory, unless you have a lot of programs opened at one time, which could also cause some of the lag and noise during page reloading, etc. Only have a few programs open and see if that makes a difference.
The shared IRQ that the audio is on could also cause some problems. Audio is always on a shared IRQ with some other higher priority device and if that device needs "service" it will interrupt the sound. One thing to try is uninstall the sound in the Device Manager then restart the PC and when Windows starts it will detect and reinstall the sound. Sometimes that will put it on a different shared IRQ and help the problem.