If this is true, then reclaim at least 277.7 MB of hard disk space (more if you have more than one software image). These software image are created whenever you restore your iPhone or iPod Touch to the latest SDK, and these software images remain on your hard disk even after the OS in your iPhone or iPod Touch are upgraded.
To delete the software images,
1. Launch Xcode
2. Navigate to the Window menu and click on Organizer menu item.
3. An Organizer window will appear. If you look at its left column towards the bottom, you’ll notice the IPHONE DEVELOPMENT section
4. Click once on Software Images and Xcode will display a new window similar to
5. Right-click on any Software Image you no longer need (e.g. because you’ve installed it to your device and you do not expect to need to re-install that version again) to reveal a pop-up menu.
6. Choose Delete Software Image to move that image to the Trash, and empty Trash from the Finder.