For the most part it won't hurt anything. The main thing to worry about when overclocking is heat and modern processors all have circuitry built in to shut down the computer if it exceeds a certain temperature. But there is always a chance of something being damaged.
Intel does not void your warranty if you OC your cpu. But if you switch out the heatsink or mod the setup in anyway, then your warranty is expired. I don't know about AMD though.
Intel does not void your warranty if you OC your cpu. But if you switch out the heatsink or mod the setup in anyway, then your warranty is expired. I don't know about AMD though.