Cpu under clocked it self?

I have a old computer that has a core 2 duo in it .it hasent run for a while but when i turn it on the cpu under clocked it self from  2.13ghz to 800 mhz ? is that normal ?

Completely normal. It's simply running slower to save power.

however If it's doing that under a load then you have issues.

I am running on load

Do you have any power saving settings on in windows?

no i dont .