its not possible, i have a 30$ card myself and it runs games at 800x600 at the lowest possible settings and barely manages 25fps (for the latest games)
how did u not find PSU, as i said its at the back of the case where the wall power goes onto the PC, it will be a small box sort of a thing with lots of wires coming out, and there will be a label on it, post a picture of that label