Hi Billy, and welcome to Tom's Hardware.
Tell us a little more about the older HDD, manufacturer, size, how formatted, if it came from a Win-XP system.
First thing to do is to have the HDD connected, both power and data cables, and boot into the BIOS, by clicking on Del, or F2 just after the startup screen. See if the BIOS recognizes it as Disk# whatever. Then go into Device Manager, and look in the Drives section to see if it is listed there, or if there is a yellow alert warning.
Lastly, RtClk on MyPC, Manage, and go to Disk Management. In the lower graphical area, review your disks, and volumes, to see if it is seen by the OS. If recognized, there will also be a colored band above the Volume status that helps identify how the partitions are set up. Does it have an assigned Drive letter?
With that info, we will be better able to help.