hey body its pretty simple. Download iphone fimware 4.2.1 and redsnow beta 6. Run the redsnow beta 6 and load firmware from redsnow. if your laptop is quad core processor then run task manager and go to the process. You will see a process running redsnow, right click on that you will see "process affinity" click on that and choose any only one processor among one then close that. Again go to the redsnow and click next and do not forget to choose iphad base band and two other check box which already checked there. Then run DFDU mode (Actually redsnow shows you the steps there). After sometimes, the iphone reboots 2-3 times and downloads the custom firmware to the iphone and reboots final time. Then you will see cyndia installed on it. go to the manage->resources and you will see repo for ultrasnow click on that and install, your iphone is ready for go.

Cheers