The power supply unit (PSU) is a box inside your computer - You Plug the power cable into it at the pack of your computer. The PSU then distributes the electricity to different parts of your computer. Better ones are more expensive but you could probably get one for £15-£20.

Open your computer and take yours out - Look at the make and model of it, and try replace it with a similar one, If you don't feel comfortable doing it, its probably best if you take it to a computer repair shop.

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