Apple have released the iOS 4.0.1 firmware for iPhone 3G, 3GS and 4. It is coming up with many improved features and fixes. They have released this iOS 4.0.1 firmware also for fixing a main problem which plagued the iPhone 4 – the Antenna Reception issue.
Now you could download the iOS 4.0.1 for your iPhone and then manually install it using iTunes or you could automatically do it via iTunes 9.2.
Download iTunes 9.2 from here.
Download iOS 4.0.1 for iPhone 4.
Download iOS 4.0.1 for iPhone 3GS.
Download iOS 4.0.1 for iPhone 3G.