With USB Loader GX you can have the games stored just about anywhere as long as you tell the loader where to find them via the custom paths option in the settings menu, for my own preferences I have chosen to keep the games in USB/GameCube and have written the guide as such, however you can name the folder whatever you want it to be. I will give the full details on how to set up the custom paths for the ISOs but first thing is first.
Go to the Homebrew Channel and load USB Loader GX, click the button at the top of GXs main screen that says "Select Loader Mode", this will be the 4th button from the left, and check the box marked "GC Games". Now make sure you have r1200 or higher, you can check this by clicking the settings button, going to page 4 and clicking credits. In the top left you will see your Devolution revision number, in the top right you will see your loaders info including loader revision, IOS revision, d2x version and Dios Mios if you have it installed. If you want all of your GC games to load with Devolution go back to the first page of the main settings, click on loader settings and scroll down to GameCube Mode. You can choose either Devolution or MIOS (Default & Customs), choose Devolution and all of your GC games will load using that now. Scroll to the bottom to turn on various settings regarding how Devolution functions.
: This function is for those who either don't own a GameCube memory card, have had their cards battery die or just for those who are too lazy to use their cards
: This function will make the games appear in 16:9 widescreen without stretching the image.
: This controls whether or not your disc drive will flicker during gameplay.
: This option is to enable direct button mapping. When using an alternative controller (such as a Wii U ProCon) the buttons are different. When the game tells you to press A you'd actually have to press b. Turning this option on will correct that by mapping the buttons to the correct letter (A=a, B=b, etc etc).
Setting the Custom Paths:
***If you installed your games using the "Alternative Method" described in Part 2 you only need to set the custom path for Devolution's Loader
In order to make GX to see and load your GameCube games you'll need to set the custom paths first. Plug your USB device into your computer, open it and create a new folder on the root called GameCube. Next open the new folder you just created and inside it create a new folder for each of your ISOs. These folders should be named for each games specific game ID number in order for USB Loader GX to see the games. Example, if you have a USA (NTSC) copy of The Legend of Zelda: The Wind Waker, you would put the GZLE01.ISO in USB/GameCube/GZLE01. If you're unsure what your games ID numbers are you can easily find them on GameTDB.com, or if you used CleanRip, by checking the dumpinfo text file generated when you ripped the game.
Now plug the USB drive and your SD card back into your Wii. Load USB Loader GX, go to settings page 2 and click "Custom Paths". Scroll down until you see "Main GameCube Path" and click on it. At the bottom of the screen you will see the following 3 buttons: "OK", "usb1:/" and "Cancel". If instead of "usb1:/" you see "sd:/" your USB is already the selected device, you only need to specify the folder, if it does say "usb1:/" click on it to select your USB device. Navigate to your GameCube folder, press A to select it, then at the bottom left of the screen click the big OK button. A pop-up will appear telling you the Path has been changed, click OK to close it.
Now you must tell USB Loader GX where to find Devolution's loader.bin so it can load the games. While in Custom Paths scroll down till you see "Devolution Loader Path" and press A on it. Navigate to sd:/apps/usbloader_gx, click the OK button on the bottom left of your screen, click OK on the pop-up message telling you the path has been changed and you're done.
Verifying & Playing Your Games:
You load the GC games the same as you do with Wii games, click the game image and click start. You can also press 1 to download the cover/disc art for any games so long as they are available on GameTDB.
Find the game you want to play, click on it and click start. Your disc drive should begin blinking twice in regular intervals. Simply insert the disc for the game you're trying to play and wait, your disc drives light should blink 5 times and then a moment later the game ISO should load. You may then eject your disc, the next time you want to play the game it will start right up off USB no disc required. Repeat this process to verify all of your games.