installing a hard drive

I havn't worked on a dell in a long time, but I remember there was some kind of combination you had to do to get it to recognize the hard drive. I thought it was put on the num lock, scroll lock, caps lock, and press alt, and b at the same time, while in the bios at the line that registers the hard drive.  It is not working for me now, and I am not sure if I am remembering it exactly right.  Anyone have any suggestions, or know what I am talking about?  The other one I worked on before was a deminsion, but I am working on an optiflex now.  Would appreciate any input.  Thank you in advance,  Bev wells