I Tried to install Yosemite on a Blank HDD, this worked, then i go back to my old HDD, to recover my data and settings,but Snow Leopard OSX doesn't start. Any help are apreciated.

My client's "MacBook Pro 7.1" has the airport connections down, so I Tried to install Yosemite on a Blank HDD,the system worked but the airport card not, then i go back to my old HDD, to recover my data and settings, but Snow Leopard OSX doesn't start.

now, i'm watching the Apple Logo and the animated little balls by aprox. 45min, and nothing happens.

So Thankfull.

Sanches, Gustavo