You will need a hex editor
(I recommend HexEdit from http://www.catch22.net/)
Step 1:
Make a backup of your up-to-date Media.pk2 file. This is very important, in case you screw up.
Step 2:
Open your kSRO (or cSRO, tSRO, jSRO) Media.pk2 file in HexEdit. Hit CTRL+F to bring up the search dialog. Make sure that the "Data Type" dropdown is set to "ANSI String". Now in the "Find What" field type in "Korean", "Chinese", "Taiwan", or "Japan" for kSRO, cSRO, tSRO, and jSRO respectively. Click "Find".
Step 3:
Look to see if what you found resembles the screenshot below. If the readable parts are shorter, and you don't see anything about "FTP" anywhere, press F3 to find the next instance. Once you are at the right spot, note the file size in the lower right of the window.
Step 4:
Press the Insert key on your keyboard or double click "OVR" in the bottom right of the window to switch to insertion mode. Clear the first instance of Korean/Chinese/Taiwan/Japan and type "English" in it's place. If you are editing cSRO's Media.pk2 file you can move on to step 6.
Step 5:
If you are editing the Media.pk2 file of kSRO, jSRO, or tSRO you must delete a byte or two to preserve the file size. Place your cursor in the hexadecimal column, as indicated in the picture, and clear the one byte for kSRO and tSRO or the two bytes for jSRO.
Step 6:
If you did everything right, your file size should be the same as it was when you started. Check it in the lower right of the window to be sure. If it is not the same, you probably did something wrong. If it is the same, you can go ahead and save the file (it might take a while) and exit out of HexEdit.
Step 7:
Now you can start up the game and test to see if it worked.
Known Issues:
This method completely disables Unicode characters in the game. If you normally launch the game with AppLocale, all Unicode characters will be boxes. This makes it hard to select your server. Instead, you should launch the game without AppLocale so that Unicode characters are replaced with ASCII characters.
If you normally launch the game without AppLocale you would have noticed that number such as those in your HP and MP bars were gone. This will fix that, but the numbers will often be staggered and look odd. I am unsure of how to fix it.
If an English translation of something doesn't exist, it simply won't show up. This is pretty much a non-issue because you wouldn't have been able to read it anyway.
In kSRO this will disable the "nude" character skins. I don't consider this an issue because I would rather be able to play the game in English than have some eye-candy to look at. Regardless, there is a way to re-enable them ingame by editing the PK2 files (also works for versions that don't support them in the first place) and I am considering writing a guide on it.
