How to Softmod Your Xbox
What you need:
A working Microsoft Xbox and controller
Your Xbox must have Dashboard 5960. Read more about that here.
A copy of one of these games:
Splinter Cell (NTSC and PAL) (Platinum Hits works)
James Bond 007: Agent Under Fire (NTSC only) (Platinum Hits may not work)
Mech Assault (may need disc serial number MS02301L)
A female USB to Xbox adapter cable
'Female', as in, you plug the USB stick INTO the cable, which you then plug INTO the Xbox controller port - not the other way around!
A compatible USB stick
To be compatible, the USB must be very old, probably from 2007 or prior - the Xbox cannot read modern USB sticks. Your best bet is to buy a bunch of used ones on Ebay and hope that one of them works.
This USB will be reformatted so make sure there's nothing on there you want to keep.
Connect your USB to the adapter, and plug it into your Xbox. On your dashboard, go to Memory. This should reformat your USB stick - usually a message will appear indicating this, but not always.
This .zip folder also contains the official manual for the Softmod Installer. If you get stuck at any point in the softmod process, refer to that guide for troubleshooting.
Plug your USB into your PC (don't reformat it if your PC asks you).
Open Xplorer360. Go to Drive -> Open -> Harddrive or Memcard. Partition 0 should appear in the left pane.
Now open the Softmod Installer folder. Extract these things:
Either Installer.zip or Installer.USB.zip. The USB version has XBMC, which is a media centre that allows your Xbox to play movies, music, etc., but takes a lot longer to install. If you don't care about movies and you just wanna game, install the non-USB one.
The Loader for the specific game you're using to softmod.
Go to the Installer you extracted. Inside its UDATA folder, there is a folder with a bunch of numbers. Drag and drop it into Partition 0 in Xplorer360.
Do the same with the Loader you extracted.
In Xplorer360, do Drive -> Close, and close Xplorer360, you're done with it. Eject your USB drive from your PC and plug it into your Xbox.
On your Xbox, go to Memory, and then Controller 2 (a.k.a. the USB drive). You should see SID 5.11 Installer, and SID5 *whatever game you used*.
Copy these two saves to your main harddrive. Afterwards unplug your USB drive, you're done with it.
Insert your game to softmod. In whatever game you're using, load the saves you copied. The softmod installer should boot when loading.
When the Installer boots, you should first backup your Eeprom. Go to Backup / Restore Features -> Create Eeprom Backup -> Backup Eeprom. Then return to the Main Menu.
Do the same with your vanilla Xbox Dashboard. Backup / Restore Features -> Create MS Backup -> Yes.
Now go back and Install either Single Boot Softmod or Dual Boot Softmod.
The difference between Single Boot and Dual Boot is that Single Boot will only let you boot to the softmodded dashboard; Dual Boot will allow you to boot to either the softmodded dashboard or the softmod installer by pressing either the power or eject buttons. Install whichever one you want.
If installing Dual Boot, you can choose what to Dual Boot alongside your softmodded dashboard, either the Softmod Installer menu or the vanilla Microsoft Dashboard. Either option is also easily accessible via the softmodded dash, so it's up to you.
You can choose to install high definition/RGB versions of your dashboard, if you happen to be playing on a high definition display.
If installing Single Boot, there are standard and virtual Eeprom versions of normal- and high-definition dashboards. I only use the basic Standard one so you're on your own for the rest.
Now you'll choose between EvoX and UnleashX (or XBMC if you chose the USB installer during step 6) as your softmodded dashboard of choice. I personally use UnleashX and have found no problems with it whatsoever.
Proceed through the textboxes. If your Xbox dashboard is version 5960 and you've made the proper backups, you should not have any problems here. Proceed with the install.
Eventually, you'll get a textbox saying to remove any disks from the disk tray and restart your Xbox. Do as it says.
If you installed the Dual Boot, you must eject the disk quickly and close the tray before it attempts to load your softmod installer/vanilla dashboard. If you load into something other than your proper modded dashboard, the install may not complete properly.
Follow the onscreen instructions and let the installer finish. Eventually, your modded dashboard will start automatically.
***IMPORTANT***: It's heavily recommended that you FTP your Eeprom to an external device such as your PC. If you accidentally lose your Eeprom, you could brick your Xbox!
How to FTP
By connecting an Ethernet cable from your internet router to your Xbox, you can use an FTP program like FileZilla to send files from your PC to your Xbox and vice versa. This tutorial will use FileZilla and UnleashX as examples.
Download and install FileZilla. Turn on your Xbox and go to your softmodded dashboard.
Once your Xbox is connected to your router, you should see an IP address in the bottom right corner of the dashboard. Input this into the corresponding field in FileZilla.
If nothing shows up, try changing your network Type in the UnleashX Settings page. System -> Settings -> Network -> Type, either Static or DHCP.
FileZilla also requires the username and password for the server it's trying to connect to (your Xbox). By default, the username and password for UnleashX is 'xbox' and 'xbox'. Input those into FileZilla and connect.
You can change these credentials in your UnleashX settings page. System -> Settings -> Network -> User and Password.
You should see your Xbox filetree appear in the right-hand explorer in FileZilla. You can now modify your Xbox's files from your PC!
***IMPORTANT***: Seriously, if you have FTP working, there's no excuse to not back up your Eeprom!!!!