If you want jailbreak iPhone 3GS with firmware 3.0 using Redsn0w 0.8. Now you can do it by using simple steps guide but you firstly must have updated or restored to the original iPhone OS Firmware 3.0 on your iPhone 3GS using iTunes 8.2 before make any move, after ward you can follow all the steps from the following link:
http://www.redmondpie.com/how-to-jailbreak-iphone-3gs-with-redsn0w/
Good luck!
[...] Step 3: Start redsn0w in order to jailbreaking your iPhone 3GS using redsn0w but firstly close iTunes. And follow the following steps to use redsn0w to jailbreak iPhone 3GS. [...]
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[...] Actually this post is not meant to review on the ability of Windows 7 Beta, instead, in this post I’d like to elaborate the steps to install Windows 7 theme on iPhone. If you’re searching such guide to have Windows 7 theme to adorn your iPhone, this post serves for that purpose. However, to install Windows 7 theme on your iPhone you need to have jailbroken iPhone first. If yours have not jailbroken, open this following link, to jailbreak iPhone 3GS: How to Jailbreak iPhone 3GS with redsn0w [...]