Quote - 280 watts is indeed very light. You might want to take a look at this page and run a calculation on what power your hardware actually draws. If it comes to more than 280 you're heading for trouble.

educations.newegg.com/tool/psucalc/index.html

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When you say  280 watts is indeed very light ,do you mean it should be more?,The Pc is an HP Compaq build date 2007, Ive looked the HP site and all that range is around 250 watts  to 300 watts for the mini tower mid range P Cs, Gaming P cs are up in the 500 watts range.
The info for the power supply I took from the inside of the PC written a sticker attatched to the power supply unit its self.

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