Why my PS3 do not read the hard drive?

Hello, From the beginning My first PS3 have upgrade error and I take the hard drive out and put in another PS3 to reformat and update to the newest version, I'm check everything work good and I put back to the first one, I turn on but when I turn its on the system on for a little and shut off. I want to make sure again, take it out put to the second one turn on it work normal. What I do wrong? why it didn't read the hard drive? Please help me... Thank you very much !!!