Expand for the links:
Download redsn0w 0.9.6rc12 for PC and Mac: http://stateofjailbreak.com/tutorials/redsn0w-0-9-6rc9-tutorial/
Find iPhone / iPod touch / iPad firmware files: http://stateofjailbreak.com/tutorials/find-iphone-firmware-files/
In this video I give a full tutorial on how to add a animated boot logo and jailbreak iOS 4.3.1 using redsn0w 0.9.6rc12 on an iPhone 3GS (new and old bootrom), iPhone 4, iPod touch 3G (16GB and 32GB models only), iPod touch 4G and the original iPad 1. The iPad 2 is not currently supported. redsn0w 0.9.6rc12 is an untethered jailbreak and works for both Mac and Windows. You can rerun redsn0w 0.9.6rc12 over your existing iOS 4.3.1 jailbreak (redsn0w 0.9.6rc9 or sn0wbreeze 2.4.b1) just to add custom animated boot logos.
If you use Windows Vista or Windows 7 then you will need to do an additional step to avoid any problems, errors or issues. Right click redsn0w 0.9.6rc12 and under the Compatibility tab select Run this program in compatibility mode for Windows XP Service Pack 3 (SP3) as well as run it as Administrator.