Original Xbox FAQ
How to connect modded original Xbox to the internet
Let's get the obvious out of the way
The original Xbox still has a normal ethernet port. The only catch is to not use a CAT6 cable as some people have issues using CAT6 with older ethernet hardware. So, if you just so happen to have your router close to where you want to set up your modded original Xbox console, just hook up a CAT5 ethernet cable and you're good to go. You can also buy an extremely long ethernet cable that can run all the way to your Xbox, but that isn't practical and you have to start drilling holes in your wall. Not to mention you've now got an unsightly wire strung throughout your home. But, it is do-able.
WiFi... yeah right?
Actually you are in luck. Microsoft did make a wifi kit for the original Xbox! And it is really cheap to find one now, but a little hard to find one with the cd needed to install it. Unfortunately, there is a reason no one buys these things. The WiFi set ups use an ancient security feature that is so out-dated, some aspects of it have been completely outlawed. This means the probability you own a router that is comptible with that technology is basically none. And just a side note, if your router does work with it, GET RID OF IT! Those routers can be hacked by 9 year olds. However, there are devices called wireless gaming adapters. This is going to be your best option.
Wireless gaming adapters
Wireless gaming adapters are perfect, well, almost. You can connect your modded original xbox to the internet via wifi and the technology is still compatible from both ends. But, it is still a little tricky to get these set up. This tutorial on How to configure your original Xbox Wifi will show you how to do so. There is also a second issue. Using a wireless gaming adapter requires it's own power cord and ethernet cable. This means if you move your modded Xbox, you gotta move all that crap with it. It's okay though, you can still internalize the thing with a little modding! Check out this tutorial on How to install internal wifi in an original Xbox console.
After it's hooked up
Now you've got your modded original Xbox console ready to connect to the internet. For most features such as online gaming via KAI or dashboard features such as XBMC media info look up and waeather reports you are good to go. The Xbox takes care of that for you. As long as you've got yourself connected by one of the means above, you don't need to do anything else.
Using FTP
Using FTP is simple too. A modded original Xbox console easily shows you your IP address in the settings and sometimes right on the main dashbord. Just connect using an FTP program on a computer that is hooked up to the same network as your Xbox, and boom, ready to go!