Your CPU should be quite alright even at 100%, as long as you have adequate cooling. You should concern yourself more with your CPU temperatures rather than load, if you're worried about hardware damage. Though at 100% utilization, you'd probably get poor stream/game performance...but that's beside the point. You should be a little bit concerned if your temps reach 75-80 C...below that, you're probably alright.
Actually, most modern CPUs will shut themselves down (blue screen) before getting hot enough to cause physical damage. Just make sure you're well-cooled.