my compaq presario desktop pc will not power on
You need to see if your power supply died. It happens. If it has died, they're on 30 or 40 bucks to replace and easy to do. Though if you don't know what you're doing, I suggest paying someone who does. If it isn't the power supply, there are lots of things it could be, all of them more expensive to fix than just the supply.
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them