Why won't my macbook pro accept an external hard drive sled?

[kingshrubb]

I took the hard drive out of my old macbook pro, bought a 3.5" SATA enclosure, and hooked my new macbook pro up to it w/ a usb cable. Whenever I turn the enclosure "on" I get this error message:
"The disk was not ejected properly. If possible, always eject a disk before unplugging it or turning it off."
All I can hit is the "okay button". :/

What can I do to get all my old important files off?

 

[spinnerlys]

Maybe the enclosure does not accept the 2.5" HDD, since it was made for 3.5" HDD.

3.5" S-ATA HDDs get their power with an extra cable, 2.5" S-ATA HDDs have power included in the small S-ATA connector. Maybe that is the reason?