Unless you want the slave to contain another OS so you can boot to it for certain purposes, all that's needed is to format it. With XP, this is done through the disk management too in the Control Panel under Administrative Tools/Computer Management. You will need to install the slave drive first, of course. Then navigate to the disk management tool and right click on the disk which will show as unpartitioned. You will need to create at least one partition and format it. The drive will now show up in Explorer and you can use it as you wish to store data. You may install some programs on it but it's usually best to run these from the primary drive and use the slave for storage.
I want to add a slave hard drive to my xp computer. do I need to install XP on to the hard drive after it has been reformated?