How to upgrade my iPhone to iOS 5?

I have an iPhone 3G with iOS 4.2.1 on it, jailbroken, and unlocked. How do I update to iOS 5? I understand that it is not supported. It's an old phone so I don't care if I brick it by accident… I just want to forcibly install iOS 5 on it.

I'm aware of Whited00r, it does not actually give you iOS 5/6 just the look of it. It doesn't let you run newer apps… I need to force iOS 5 to install. How?

Added (1). I can take Windows 7 and force it to install on my old pentium II from 1995, it will just be really slow and unstable… So I must be able to do the same with my iphone 3G and iOS 5… I don't care if it's slow and unstable I want to do it anyway… Nothing is "impossible" with technology.

I have the iOS 5 IPSW meant for a 3GS now how do I force it to install on my 3G?

Its impossible to get ios 5 on a iphone 3.