I5-670

HI all

maybe someone here can help me. I have a system i build recently using an i5-670 processor – should be blindingly fast but for some reason (using xp) often but not always the system seems to sort of freeze, when it does this the HDD lights are going like the blazes.
I have turned off indexing and now am at a bit of a loss what is causing it.
And no it cant me virus or malware as the system was just build and has only new software on it

thanks in advance