Glad to see we are going in the right direction . Things i would look at are : IRQ's . Right click my computer /properties /hardware tab/ device manager/View(at the top)/ Resources by connection / IRQ . Post the list of IRQ's here . I wouldnt be suprised if your sound card and nic/videocard are sharing .
Make sure your motherboards chipset drivers are up to date .
Make sure its not a heat issue , with summer here people are going to start seeing more termal issues . If possible go into the bios and look for hardware monitor. Post temps here . I would take a look at the fans and heatsinks inside the case , might have something plugged .
Sound card ,check for any driver updates , make sure you are set at 3/4 sound acceleration . Start/Run/ type dxdiag / sound tab/ move slider 1 notch to the left ( standard acceleration) .