Check where the main input cable goes, and there should be a big fan beside it. Take off the Computer side cover and there should be a box 9 x 6 x 4". On the side there should be a description, like 'ATX 12 volt' 'with 'PFC' etc. Then there should be a data sheet in small writing with wattage, etc. beneath the description. Depending on what card you bought, think about a minimum of 400 watts.
This is probably an easy question to answer, but I'm a n00b so here goes: I just bought a video card, cost me like 300 dollars and I was wondering if I would need an extra power source to run it. To find this out I need to determine what kind of power source I already have in this cheap wal-mart computer, so can anyone help me? Or is there anything else I need to know, maybe I'm going about this wrong... any help would be greatly appreciated!

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