1.) What OS are you running?
2.) Is this a new drive, or was it previously installed?
3.) Does the drive show up in BIOS?
4.) Does the drive show up in the Storage Utility? (Right click on "My Computer, click "Manage", navigate to the "Storage" utility.)
If the answer to 4 is Yes, then you'll most likely need to just format your drive, and it will show in Windows Explorer (assuming you're using Windows).