iOS 5 发布正式版，付下载地址

• iPhone 3GS
• iPhone 4 GSM
• iPhone 4 CDMA
• iPhone 4s
• iPad
• iPad 2
• iPad 2,2
• iPad 2,3
• iPod touch third-generation
• iPod touch fourth-generation
• Apple TV second-generation (iOS 4.4)

如果已经用iTunes下载
去这个目录
Mac: ~/Library/Application Support/MobileSync/Backup/
Windows XP: \Documents and Settings\(用户名)\Application Data\Apple Computer\MobileSync\Backup\
Windows Vista 和 Windows 7: \Users\(用户名)\AppData\Roaming\Apple Computer\MobileSync\Backup\