It seems like you want to flash dd-wrt to your WRT54GS v6 router. Am I right? If so, this is not the right forum. You should post it on the Broadcom forum. In the post, please be more specific such as at which step of the wiki that you are facing problem. Also, don't forget to take a look at the Peacock Thread: http://www.dd-wrt.com/phpBB2/viewtopic.php?t=51486
I don't understand why you suddenly work on extracting the Firmware on your last post. It doesn't seems like it has anything to do with flashing. The Firmware modification kit is used only if you have a need to modify the firmware. If you really want information on the firmware modification kit, you should start another thread instead of mixing it with your original thread on flashing. There is a better wiki on the firmware modification kit, please take a look at this two wiki: