Apple released iOS 5 at WWDC along with iCloud and Mac OS X Lion.However, to download iOS 5 you need to install iTunes 10.5 beta.

iTunes 10.5 beta is only for developers.

Earlier today Apple had released iTunes 10.3 for Windows and Mac which supports “iTunes in the Cloud” feature.



iTunes 10.5 beta comes new user interface,minor graphical changes which is similar to Mac OS X Lion and settings of panel to enable automatic downloads

Registered developers who pay a subscription of $99 a year can download iTunes 10.5 beta.

Download iTunes 10.5 :
Mac
Windows 32-Bit
Windows 64-Bit

Download iOS 5 :
iPad
iPad 2(Wi-Fi)
iPad 2(GSM)
iPad 2(CDMA)
iPhone 3GS
iPhone 4(GSM)
iPhone 4(CDMA)
iPod touch 3G
iPod touch 4G

Now open iTunes that you downloaded above and restore using your firmware.