I am using a recently updated iPhone 3GS 4.3.3 and this is how I jailbroke it using redsnow on Windows 7.
Prerequisites
- iPhone 3GS 4.3.3 Firmware
- iTunes
- Redsnow
- Internet connection
This is fairly simple
- Install iTunes
- Make sure your iPhone is updated to 4.3.3
- run redsnow
- Browse for and select the 4.3.3 firmware file and press next(requires Internet connection)
- Select install Cydia, press next
- Follow the instructions to put your phone in DFU mode (on windows I had to do this twice because windows 7 first looks for updated drivers on the internet)
- wait until redsnow shows done
Thats it, your iPhone reboots with cydia installed