this program is the absolute best, and it's free. It downloads very quick, and analyzes your entire configuration in about 1 minute! Print and save your results, you'll end up referring to it quite often in the future. It runs right in your web browser, so all information is secure. It also details all of your installed software's serial numbers. This alone has been really useful! Good Luck!
http://www.belarc.com/free_download.html