Hard Drive spinning but not being recognised!!!!

goku1234567890

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So i returned to my home after 2 to 3 months and started using my usual system and then i remembered i had an another p4 (not used for 4 to 5 months) and i thought of selling it because it was useless. I plugged it in and started it the PC started up but the CPU fan was not spinning and Hard drive was spinning but not not being recognized. So I plugged the fans wires with the correct one and it started up still Hard drive was spinning but not being recognized. please help me to repair my hard drive i don't know what's wrong with it.