Piriform Speccy is a very easy to use free program for knowing what is inside of your PC. You no longer have to download multiple programs to see what kind of RAM, CPU, Hard drive, and motherboard you have on your PC. You can just download and install Speccy on your PC.
Run it, and it gives you a summary on what is on your PC. If you need more details like drive space, real time temperature, error rate on drives, etc you can just click on the individual links on the program.
It is made by Priform who is the same company which makes CCleaner, Recuva, and Defraggler which are all great products which are free.
Download it at :: http://www.piriform.com/speccy