I modded a broken original gameboy into a hard drive case. The power light comes on when hard drive is plugged in and flashes when data is being transferred. The gameboy doubles as a cool way to store a game boy game I turned into a memory stick a while back. The build cost around f40 in total, f30 worth of which was the hard drive. This is me writing up a past build, before I ever joined instructables, I apologise for lack of photos.
Step 1: Choosing the Hard drive
I had originally planned to use an internal hard drive and a SATA adapter but turns out an external HDD is much cheaper. So this build is a hard drive in a case, in a case. Redundant I know.
How much you want to spend is up to you but more important than the storage is the dimensions. The game boy has dimensions of 90 mm - 148 mm - 32 mm (3.5' - 5.8' - 1.3) but inside the case you have significantly less room, the depth is limited by where the "game slot" and the length also has to allow room for a usb lead. As a result both the hard drive and the lead need to be super slim. I went with the Sonics 750GB as a budget option.
If you don't want the lead permanently hanging out like a tail, you will need a male to female adapter, depending on what the plug is on your chosen hard drive and lead. For example if it is a micro usb slot on the hard drive, you need a male micro usb to female "whatever the end of your usb lead is". And make sure to do the maths of whether the length of the hard drive plus the adapter will fit. I couldn't find an adapter that would be flush with the case, and if it wasn't flush it wasn't worth the extra effort. Also you will have to cut out a square for the usb socket, whereas the cable fits through the headphone cable.
Step 2: Gutting the case
Nintendo products use awkward screws so you need a special "triwing" screwdriver. You can pick one up on ebay for a quid. There are 4 screws, all found on the back and they come out pretty easily. Once you get that off, you will see the inside has two circuit boards, connected to each other by a flexi-strip from the screen. You can cut this to make working with the two parts easier. The circuit board is held in by small philips screws, these took a while to budge but bit of elbow grease and they come out. The buttons and screen are weakly glued in, you can just push these out. You now have the circuitry and the empty shell of the case.
Step 3: Carving out space
The inside of the case is full of plastic rods that the screws went into. These need cut out, along with the square battery holder. I used my dremmel for this, the rods were cut easily enough but the battery holder required more thought. I used pliers to pull out the metal and the springs and when cutting out the box I was careful to not anything needed for the battery cover to slip in and out of. This step is pretty simple, just keep carving away at the inside of both pieces until your case fits. But be careful not to slip and go through the case and also don't cut anything used to hold the buttons in place.
Step 4: Replacing screen and buttons
The screen can be pulled away from the circuit board and glued in place in the case. The "ext. connector" and "dc" connector holes leave ugly gaps which need plugged. They are attached to the circuit board and can't be as easily pulled away. Cut around them using scissors and glue them in plac. Final step is the buttons, I wanted them to be "clickable" so the Game Boy looked operational. The +, B and A buttons are plastic shells, with a rubber backing. Drop the shells into place and glue around the edge of the backing and put it on top. The select and start buttons are just backing so glue them in similarly. This method sounds flimsy but I've attacked the buttons as a "stress test" and they are secure.
Step 5: Flashing LED
Most external HDD have an LED built in. Chances are it wasn't built to be opened so have a look at how yours is put together; I got the case off mine using a screwdriver and a bit of ignorance. Find the LED and use wire cutters to snip it off from the board. Place you hard drive in the case to guesstimate how much you wire you need to extend the LED into the power light position. Take the HDD back out then solder two wires at one end to where you snipped and at the other end to the LED. Plug the HDD into a computer to check the LED works.
Step 6: Put it all together
All that's left is to put it together. Place the HDD in the case, connect the USBr lead so that the lead comes out of the headphone socket, place some glue along the edge of the case, place the LED under the power light and click the two pieces together. And you are done, you have a Game-Boy that is actually an external hard drive.