It seems to be covered but in condensed form you have four options
Softmod via game
This is one of the three games wyndcrosser mentioned, the basic idea is you use a specially hacked save with one of those games. The trouble comes in getting the save on the console.
You can use an action replay and a memory card. Neither are especially difficult to find if you can wait a while.
You do have alternatives though- the action replay is little more than a fancy USB adapter and software backend. You can then rip apart a USB extension cable, slice into the controller wire, solder like coloured wires (there will be an extra yellow wire in the controller- leave it intact) and use the controller as an action replay of sorts for a memory card or if you are lucky enough to have a compatible USB drive then you can use that instead.
If you know someone with a modded xbox then you can get them to stick the saves on something and avoid the action replay.
http://www.aid.xbox-hq.com/index.php?title...nstaller_Deluxe has a fair bit on this. Indeed softmod installer deluxe is probably the best/easiest way to softmod an xbox.
Softmod via hard drive hotswap
If you wanted this could also be a fourth method of getting the save on there but that is a roundabout way if ever I heard one.
The xbox hard drive in unhacked mode (important note at the end of this section) uses a little used feature known as drive locking, to work it has to unlock so if you are good you can pull the drive when it unlocks and shove it onto your PC which at this time is running a special version of linux (xboxHDM) at which point you can transfer the necessary files.
There is a second option with a modded xbox and hotswapping there but I advise against it.
Some links/discussion in this thread:
http://gbatemp.net/index.php?showtopic=210693
Hardmod by modchip
This replaces the BIOS with a custom one, as pretty much all the protection is courtesy of the BIOS......
You can if you want, I would consider it long and hard though as chips are fairly hard to find at a decent price.
Hardmod by TSOP flash (everything but 1.6 model xboxes)
Older model xboxes have a flashable BIOS which you can flash by bridging some points on the motherboard. All the fun of a modchip but without the cost. Most people count TSOP and modchips as one (indeed I first typed three methods for the first line)
http://www.xbox-linux.org/wiki/TSOP_flashing_HOWTO
Modchips vs softmods- remember drive locking, not all drives can do it (
http://xboxdrives.x-pec.com/?p=list ) and as softmods load fairly late in the boot cycle the drives needs to be locked for the softmod to work. Modchips/TSOP flash dodge this.
If the auto installer deluxe disc does not have what you are looking for (doubtful but it can happen) then FTP is what pretty much everyone uses (xbins and the previously mentioned frontend autoxbins will sort you there), USB is possible but it is stuck with the same limitations mentioned in softmodding not to mention it is USB 1.1 and so very slow (about 400K/second- enough to watch an xvid show just about).
Games can be burned to disc and if you are talking about media playing XBMC supports just about every streaming/network sharing protocol going (most people just use SMB but it has others).