I personally do not trust any shipped Hard Drive including ones shipped with brand new CPU. Zero-formatting (low-level format for SCSI) Hard Drive will map out bad sector, and will save steps of troubleshooting down the load.

1. Go to Application Folder > Utilities Folder
2. Launch Disk Utility Application
   Alternatively, open Spotlight with Cmd+Space then start type Disk U... then Disk Utility will be listed for your to open there.
3. Click on [Erase] Tab
4. Select the drive you with to format
5. Choose Format type to Mac OS Extended (Journaled)
6. Click on the Security Options button
7. Select Zero Out Data option