Why does Bitcoin-Qt use all my CPU? Can I prevent it?

[bujiraso]

I see a few threads posted about this by other users where bitcoin-qt wallet takes up nearly all or all of the CPU usage available.
I'm not mining or anything, to the best of my knowledge. Is there some way I can tell it to cool it?

[bujiraso]

Actually, I solved it. Turns out I had indeed told it to try mining.
Nevermind.
Would delete thread but I can't; turf it if you want, mods.