Could you post a screenshot of your Disk Management (diskmgmt.msc) window showing the layout of all HDDs? This will better help us in determining what may be wrong.
Is it SATA or IDE? If IDE did you configure the jump settings correctly? Did you connect both power and data? Go into the BIOS menu and see if it is there.
Try disconnecting the primary drive and booting with only the new drive. It won't boot but the BIOS should recognize it. Then, shut down and reconnect your primary drive and reboot. Both drives should be available.