- Joined
- 2 Aug 2005
- Posts
- 8,721
- Location
- Cleveland, Ohio, USA
Open up the disk utility in Applications -> Utilities, click your disk, and select Erase. You'll need to choose a file system. If you need the HDD to work with just OS X use Mac OS Extended (Journaled). If a Windows machine needs to use it too occasionally, use MS-DOS file System.
