If it were me, I'd get a known quality-brand power supply in the 350W+ range regardless of what else may come to light. The "P4-ready" sticker probably is trying to convey that it has a four-pin ATX12V power cable, which I hope you have plugged into the receptacle to the upper-left of the CPU socket
(the board usually doesn't run at all if it's not, but hey). Anyway, an Enermax, Antec, Sparkle Power or Fortron unit might do well for you. I'm a fan of Antec, partly for the three-year warranty and ease of finding one available at stores, but I have an Enermax too.