If you want to run a free diagnostic and inventory report on your system, then check out Belarc Advisor.

The Belarc Advisor builds a detailed profile of your installed software and hardware, missing Microsoft hotfixes, anti-virus status, CIS (Center for Internet Security) benchmarks, and displays the results in your Web browser. All of your PC profile information is kept private on your PC and is not sent to any web server.

I downloaded, installed, and ran the report in under a minute. It breaks it down by area: operating system, system model, processor, main circuit board, drives, memory modules, users, local drive volumes, network drives, printers, controllers, display, bus adapters, multimedia, communications, other devices, virus protection, missing Microsoft security hotfixes, installed Microsoft hotfixes (by product), software licenses, software versions, and a System Security Status score (x.xx out of 10) with details!

Best of all, it's free!