This version of iOS is intended only for installation on development devices registered with Apple’s Developer Program. Attempting to install this version of iOS in an unauthorized manner could put your device in an unusable state, which could necessitate an out of warranty repair.
Download iTunes 10.5 Beta 5 for Windows and Mac
As you might know that Apple has released iOS 5 beta 5 for registered developers. Alongside with that, Apple has also released iTunes 10.5 Beta 5 which is required for syncing devices on iOS 5 Beta 5. Registered developers can get both iOS 5 Beta 5 and iTunes 10.5 Beta 5 from their accounts.
If you are a non-developer, you can get a subscription worth $99 per year from Apple’s Developer Website and get access to a wide array of content geared at developers, such as documentation and exclusive tools as well as, of course, pre-release builds of iOS.
Please note that to run iOS 5 beta 5 on your iPhone, iPad and iPod touch, you will need iTunes 10.5 beta 5. iTunes 10.5 beta 4 will no longer work with iOS 5 beta 5 restored devices, and you will not be able to sync if you don’t install the latest iTunes pre-release beta on your Windows or Mac.
Warning : Apple warns non-developer from using iOS 5 beta 5 :
So refrain from installing iOS 5 beta 5 by illegal means. Rather wait for the iOS 5 final which is expected to be released this fall