2nd SATA hard drive not recognized

Working with an Optiplex 780 running Windows 7 Pro with 8G Ram. Trying to add a second SATA hard drive.  The drive has been formatted NTFS, and is recognized by the machine if I use a USB drive adapter. However, when I put the drive in the machine and connect the power and SATA cable it is not recognized. The machine has one SATA drive and a SATA DVD which use two of the SATA connections on the mother board. There are two others... I have tried both... but no luck. What am I missing here? Suggestions welcome. Tomster2

Have you tried this here,

"When you see the Dell splash screen, Press F2, go into your BIOS, Highlight the drive and press enter to enable it. Then save and exit into windows. Then go into Control Panel, Administrative Tools, Computer Management, Storage, Disk Management. Then right click your new drive, select format. From there you can assign the drive an letter".

If that does not work, then you might try running your dell diagnostic from your drivers disc, or by Pressing F12 at boot, if you still have your partition. This will check to see if you have any problems with your ports on your motherboard.

Is the new drive seen in BIOS Setup?

What happens if you disconnect the SATA cable from the DVD drive and connect that cable to the new hard drive?