Mac OS X 10.6: About System Profiler
System Profiler provides information about your computer, such as the hardware and software installed, the serial number and operating system, how much memory is installed, and what peripheral devices are connected. This information can be useful in troubleshooting problems that might occur. If you call Apple Support, you may be asked to provide information from System Profiler to help diagnose the problem.
For more information about System Profiler, open it and choose Help > System Profiler Help. To open System Profiler, choose Apple Menu > About This Mac, and then click More Info.