How do we know that when we buy a memory chip ( Say A-Data DDR2 1Gb Ram ) for 667Mhz , the computer is running at 667Mhz and not otherwise ?.

if you know what speed ram before you put the chip in just add

Use SiSoft Sandra or PC Wizard 2007

U will know how much your chipset and your RAM could actually go and what they support.

You might also want to try CPU Z which will show you almost everything about your hardware even the realtime running CPU speed, FSB, clocking, and types chipset. It is really worth the download.