I figured it out that my motherboard lists usb drive in hdd even though it has USB booting. I'm gonna try this once again. Thanks!
EDIT: I followed the instructions, but same screen is displayed
EDIT2: I managed to burn mountain lion to a DVD and it successfully booted, then on restart it froze on apple logo screen with an exclamation icon over it and the spinner stopped too. I restarted the PC and it froze again so I restarted again. Now I'm in a desperate situation since on the 2nd restart my monitor didn't show anything, PC started like normal, no beep, all fans running but nothing displayed. So I'm at a point where I don't know what to do. I tried unplugging the cable and letting it sit for 5 minutes just in case it would have been on sleep, but nop. It's weird that such thing could happen.