I know how to boot off a cd or dvd..... my question is what is the program the Apple genius use? Also i know that the system disc that come with the macs have diag software on disc one, and to run that you hold down "D".
D is to force the computer to use the internal hard drive as the boot disc. You could call and ask what they use to diagnose issues, but there are several freeware of shareware programs that can diagnose issues. You can check this link: Pure Mac: Diagnostics, Maintenance and Repair - Software for Macintosh
there's actually different diagnostic tools that are used for different problems. the all in one diagnostic/optimization tools really don't tell much other then mac/pc specs and what has been changed. this includes the proprietary diagnostic tools that the geniuses use.
the best way to look for a diagnostic tool would be to first determine what you're having problems with and finding a diagnostic specific to that problem.
please keep in mind that there are some diagnostic tools that work better with specific hardware configurations and chipsets...