Windows 7 Tip: 
Blackra1n RC2 is Live now to Jailbreak iPhone 3.1.2 3GS in Windows and MAC both. It will help you to jailbreak all iPhone’s (2G/3G/3GS) and iPod touches (1G/2G/3G) running iPhone firmware 3.1.2. Don,t forget to Check some other Tools to Jailbreak and Unlock iPhone here.
Whats new inBlackra1n RC2 :-
Fixed 3G issues
Tethered jailbreak for 3.1 OOTB ipt 8GB and new 3GSes
Fixed Icy issues
Both Windows and Mac
Download Blackra1n RC2 For windows and MAC here
It didn’t ra1n with RC1 and it’s still not ra1ning with RC 2 3Gs 3.1.2 Apple wins blackra1n sucks.
Worked perfect for me. First time I tried.
OMFG! it fricken worked with the first try. hahahaha im shocked it only took like 5 seconds. thank you very much. I LOVE THIS SITE. PEOPLE IT REALLY WORKS im a real person living in hawaii. it really works. THANAKYOU. *the only thing, it looses your contacts and cydia LOL. but who cares you can always reinstall
IF YOU HAVE A 3G-S, DO NOT use this software yet- Blackra1n RC3 makes your 3G-S phone stay stuck in recovery mode if you restart or turn off…quite a huge flaw. I will be restoring and waiting for something that won’t screw up my GPS, youtube app, and make my WiFi stop working randomly, requiring network resets everytime the phone is restarted- too much work and trouble. I’ll be waiting for something better, and plan to donate towards that goal- the software worked FLAWLESSLY on my older 3G.
Unless you carry your laptop with you everywhere, and are willing to run Blackra1n RC3 and do full network resets again every day, skip this one and wait for a better version. Apple, you bastards win this round…damnit.