The patch in the first post doesn't seem to work for the kindle wifi as the file is different and I can't find the lines of modify.
For those who want to know how to access and modify the file, you need to jailbreak your kindle, then enable USBnetworking. This thread explains
how to jailbreak. And a filed is attached to that thread which allows you to enable USBnetworking.
This post has instruction for USBnetworking for the kindle 3.