Download Jailbreak iOS 4.2.1 Using Redsn0w 0.9.6rc7 On Windows

Right click on the shortcut, select �Properties� and go to the �Shortcut� tab. Edit the command to reflect your current IPSW firmware. Replace �iPod4,1_4.2.1_8C418_Restore.ipsw� to the exact name of your device�s firmware. Extract the Redsn0w 0.9.6rc7 zip file and copy Redsn0w.exe, the shortcut �boot-ipt4g� and your iOS IPSW firmware to C drive.When you double click the shortcut, Redsn0w will automatically process the IPSW so that you don�t have to select it manually and select the �Just booth tethered now� option (the �j argument in the command). So you are directly taken to the screen where you put your device in DFU mode.
All download links given at bottom.
The shortcut �boot-ipt4g� points to the following command:

C:\redsn0w.exe -j -i �C:\iPod4,1_4.2.1_8C148_Restore.ipsw�

Download Jailbreak iOS 4.2.1 Using Redsn0w 0.9.6rc7 On Windows