You'll need to add more information to your post.
Once you add the hard drive to the machine, you will need to format it.
If you plan to use the hard drive under MS Windows, then you will need to format it with either FAT32 or NTFS.
If you plan to use it under GNU/Linux, then there are many filesystems you can format the drive to, (ext2, ext3, ReiserFS, XFS, JFS), this is why you need to specify what you plan to use the hard drive for.

If you use it under MS Windows, once you format the drive, it should be ready to be used under the system.
If using the Hard drive under GNU/Linux, then after you format it, you'll need to make some changes to the /etc/fstab, to mount the drive during boot time.