have tried overclocking it? often attempts to overclock a CPU can make it revert to a much lower clock speed as a safety mechanism. If it has always been like that then you can try going into your BIOS and seeing if there are any options for your CPU or you can check to see if it says the CPU is the correct clock speed or not.
I recommend you download a program called CPU-Z and take a screenshot of the first tab, it shows the information of your cpu and will help us diagnose what exactly is wrong.
To take a screenshot:
make sure that the CPU-Z window is your active window
hit ALT + Print Screen (usually above the delete and insert keys)
open up Paint (mspaint to be exact)
hit ctrl + V (this is the hotkey to paste)
the screenshot of CPU-Z should be there
just save it as a jpg and upload it onto
http://imageshack.us/
then just paste in the link
I'm sorry for treating you as if you know nothing about computers but it is what I do to make sure no one misunderstands my directions.