Hi Baltan,
1. first things first... you should unplug your computer and leave it off until you replace that power supply to avoid any further damage or risk of fire
2. based on you first post, as I understand it your computer turns on and runs but you have no sound and no USB power? If that's the case, then your motherboard may have also been damaged by the dying power supply.
3. since you saw smoke come out of the power supply, it's certainly time to replace it. you say your original was an ATX, so you can replace it with another ATX.
generally speaking, any power supply that blows smoke out of it is a cheap power supply. a quality power supply has good protection circuitry that shuts it down before it gets to the point of blowing out smoke (or even worse, catching on fire).
you have just learned the importance of having a good quality power supply. so when you get another one, don't just buy the first one you see. brands like Antec, Enermax, and Fortron make low cost models (as well as higher end end models) that will protect your PC from damage.
good luck :wave:
