Ok, many people got it today, the answer was "Cold"
I am a state --> being cold
yet I am all over the world. --> there is cold all over the world
I can kill if exposed to me for too long --> Pretty self explanatory
yet I can also make people happy by what I bring --> Cold brings snow, and the possibility to do winter sports and such.
I make people change the way they live, at least for some part of the year. --> Because of the cold, people wear jackets and heat their homes, they also change tires on their car, etc.
When my presence is not too strong, I'm often called cool. --> Cool is an adjective to describle something a little cold.
I have a bolt --> Cold bolt is a mage skill,
tough I am not man-made. --> Cold existed before man
My name can also mean a virus and I don't think anybody likes having me! --> Having a cold, not fun!
Note: If you're name is not on the list but you had sent the right answer, it's probably because you forgot your in game name, I was pretty clear on this, think about it next time! Also, don't forget to put "Riddle" as the title, I wont accept entries that don't have this for the next riddle.
The winners: Alexander (IGN Alexander) (Our first winner!)
Vivi (IGN Ichigo) Clemie (IGN Clemie) Jubei (IGN enna) Manifus (IGN -Neo-) YetiPunk (IGN Avoroth) Tenshi (IGN Black K. Night)
That's 7 winners, so they each receive 143k. I wont be there for a few days however, so you'll have to be patient ^_^