If you have downloaded iOS 5 beta, you must first activate your idevice to run it. Activating firmware means is that you have to get the UDID of your device and get it registered with the iPhone Developer Program before you can start (legally) loading beta firmware on it and you don’t face any problems while synchronizing with iTunes. Installing beta firmware on unactivated device will make it useless. Here is how you can activate iOS 5 beta 1.
How you can find the UDID of your iPhone, iPad and iPod touch for iOS 5 activation. UDID of your device must be registered with the Apple Developer Program before beta firmware installation on it. Because iOS 5 is in beta phase right now, you need to register the device UDID, and here is how you can find UDID of your iDevice.
If you are not a developer and still want to try iOS 5, then use this tutorial but at your own risk. Here is how to upgrade and activate the iOS 5 firmware without a developer account UDID. This iOS 5 hack was discovered Mert Erdir and exploits a security flaw in the activation screen. If you want to run the iOS 5 firmware, we recommend you to save your SHSH blobs on the iOS 4.3.3 firmware because if you encounter any error in the process you will still be able to downgrade your iPhone back to iOS 4.3.3. This method will only work for the iPhone.
Bypass the activation process and run iOS 5 firmware. This hack will not work on the iPad 2. On iDevices with a cellular modem, this may permanently upgrade your baseband, and will also prevent activation with your carrier as you are bypassing it. This method is not a jailbreak, but after using it you can use iOS 5 beta without activating it. This iOS 5 hack exploits a security flaw in the activation screen. Requires no hacking or jalbreaking and is super easy. Here it is: