I was wondering why POST beeps weren't covered. I think the beeps will usually tell you what's wrong, especially useful if there's a memory issue.
I know we discussed POST beep codes in one of the troubleshooting segments, but I cannot remember which one. I specifically remember pulling up the Dell documentation for an OptiPlex 745 to interpret a beep code as well as explain the diagnostic number lights on the front of the case.
Sorry I couldn't be more helpful. I will ask around the office to see if anyone else can pinpoint it.