The computer can use any standard ATX power supply unit (PSU). I recommend that you consider one that is modular. This will allow you to use only the cables that are absolutely necessary which will allow for better airflow. I like Corsair products. Since the existing PSU is 500W, you must be considering adding a more powerful video card. This will require better airflow.
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@Ppetsku96, I suggest measuring the existing PSU and comparing the measurements to the one in the link. Some of the higher wattage PSU's are made larger. Also, you could get by with less wattage. The computer configuration is not going to allow for enough upgrades to require that amount. If it were me, I would buy one with no more than 800W. Just a suggestion.
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