I'm not sure I understand the title of this thread, but our FAQ is awful isn't it? A good percentage of the questions are recurring and could be answered by a decent FAQ. I've made up my own FAQ and copy & paste answers from it like the following:

It could be the infamous Dell Ground Loop. Symptoms would include a scratchy staticy noise when moving the cursor, and the noises occurring only when the computer is plugged into the power adapter and connected to another device (like a mixer, power amp, etc) that is also plugged into a/c current:

1. Eliminate the ground either on the computer or on the other device it is connected to, by using a 3 prong to 2 prong adapter, but just as a diagnostic measure because this can be dangerous and could invalidate warranties. See Rollie's stickie cautioning against defeating safety devices.

2. Isolate the grounds from each other by using a ground isolator or a direct box with ground lifter. Some members have given us positive reports on Radio Shack's $16 Ground Loop Isolator (270-054). There are other such devices available for more money which would probably be better for someone doing pro audio work.

3. Or use non-conducting material to connect the 2 devices; specifically by using optical spdif to transfer the audio signal rather than copper cables. This would require having an external soundcard that has optical spdif.

Jim