You don’t have developers account, and you want to install iOS4 now! But dont worry now its possible to install iOS4 without developers accounts. But the main problem is you need a mac machine for this, If you do have a OS X machine, read on. Why the Mac component? iTunes 9.2 is required, and as it stands that iTunes build is Mac only. You do not need your UDID to execute the installation.
How to install iOS4 in Mac
3. Plug in your iOS device, and then tab over to iTunes. In iTunes, alt+click on the ‘restore’ button, and then when promoted to locate the file select the IPSW file we just moved to your desktop. Wait for between 10 and 15 minutes for the new OS to be moved over.
and Bingo! 😉