Hard disk spread spectrum effect?

Google is your friend !  

Google me up baby !

as much as i should be saying "google it your lazy bum", i too once wondered what it was.

Its to make the boards meet the world standards, when you run your cpu at 2000mhz thats a frequency and if something else is using that frequency, it might upset it (tv's, radio's and other electrical devices) - spread spectrum changes the clock speed and variates it to say 1997mhz to 2002mhz to avoid disruption.

Aparently overclocking with it on causes more instabilities earler, and its generally not needed, or not at all.