Is this for a NEW buy, or an existing one. If new gracefully is correct - make sure you verify. I have a toshibia A305 and ther is a place for a 2nd HDD and the pin-out are there - just NO socket. Come on a dollar two nity-five part. Thought about having the socket installed, but no sure the BIOS would recognize it and most bios for laptops are Locked (Min user settings).
I have a Toshiba Qosmio X305. It came with 1 HD installed. There was room and a connector for the 2nd HD, but no mounting bracket. I got the bracket for $5 from Toshiba Parts. No one else had or knew about the 2nd HD bracket.
Also depending on the laptop, you may have either a firewire or eSATA port. Those both would allow you to use a 2nd HD. External USB is also possible but much slower.
Check you laptop specs, see what is available from there.