Windows 7 Tip: 
If you’re looking for an exquisitely detailed audit of your hardware, then you have to try Belarc Advisor Free Pc Audit Tool. It starts with the basics, such as the computer manufacturer, installed RAM, hard-disk size, and processor type and speed. But it also shows you the motherboard maker, hard-disk manufacturer, chassis serial number, PC service tag, bus type and speed, multimedia devices…the list goes on and on.
Not only does it analyze software and operating system components and tell you where problems are, but in its comprehensive report it tells you what your computer’s physical components are: not just how much RAM you have, for example, but what kind of RAM and which slots are occupied.
Download Belarc Advisor
How does it compare to this tool that you can use online. PC Audit Tool. The difference is negligible in my opinion.