Static on internal sound system

Update on static problem. Appreciate the suggestion that it is a keyboard problem, or the start of HD failure. Replaced HD. No positive effect. Tried suspending keyboard in air (incorrectly installed or pinched wire). No positive effect. Static continues. Tried CD. optical works, but dialogue window says that Itunes is corrupted. Asks for reinstall. Internet connect to streaming no go. Programs without sound, no static. Running osx install disk with music and narrative-static. And the popping noise increases progressively. Reminds me of old vacuum tubes, getting worse as machine warms up. Any suggestions