How can you tell what components are in your PC without taking it apart?
There are some system reporting tool programs that give a good snapshot of the components of the computer, and the software installed as well. This is particularly useful if you need to find out the model of the motherboard that is in the machine, so you can find out what memory it needs, or source the correct BIOS or driver updates.
CPU-Z http://www.cpuid.com/cpuz.php
Belarc Advisor: http://www.belarc.com/free_download.html
SiSoft Sandra http://www.sisoftware.net/index.html?dir=&location=downandbuy&langx=en&a=
Speccy http://www.piriform.com/speccy