Hardrive Problems

Hello,
I have a computer that runs Windows Vista and it boots up just perfectly. I then took a hardrive out of my old computer and connected that right below the exsiting hardive of the Windows Vista computer. Then when I turn on the computer and after its on for awhile a measage appears that says Non system disk or disk error relpace and strike any key when ready.

I then unplugged the hardrive and restarted the computer with the exsisting hardrive that was in the computer and then it workes just fine. So my question is, Is there anything wrong with the second hardrive im trying to put in my computer? Or what does that Error measage mean ?