How to install a secondary Serial AT Attachment hard drive you are asking yourself?. If both your hard drives are Serial AT Attachment, then what you will do is use a Serial AT Attachment cable numbered “1” for your primary hard drive. Then you will want to use a second Serial AT Attachment cable numbered “2” for your older secondary hard drive.
Serial AT Attachment cables are marked with numbers. You can try to boot your computer up with your hard drives configured this way and it should work. If that computer does not boot or boots off the wrong hard drive, then you can go into the computer’s Basic Input Output System and make sure your boot order is correct.
Your new 1.5 terabyte Serial AT Attachment hard drive should be listed first with your older hard drive listed second. You can read this adding a hard drive Hewlett Packard web page that shows you how to add an additional hard drive to your Hewlett Packard system, so that you have both hard drives configured correctly. If all goes will this will allow you to boot off your new 1.5 terabyte hard drive and be able to access some data off your old secondary hard drive.
If you want to be able to switch back and forth and boot off each hard drive then that will require more diligence and is beyond the scope of this article. These instructions were written for a Hewlett Packard Media Center M7250N desktop personal computer with a new secondary 1.5 terabyte hard drive, but can certainly be used as basis points for adding a secondary Serial AT Attachment hard drive into other desktop personal computers.