You can mod your Nintendo DSi to play Nintendo DS and Game Boy Advance games. You can also download and add games that are available online for free. To do this, you will need an R4i card, which has a MicroSD slot and a MicroSD reader for you to slide into the USB slot on your computer. You will need the R4i card and MicroSD card to transfer firmware and DSi games to the DSi console. You will be playing your games in no time.
Remove the R4i card and MicroSD reader from its package. Slide the Micro SD card into its slot on the MicroSD reader.
Plug the MicroSD reader into the USB slot on your computer. Go to "Computers" and open the MicroSD card file window. Minimise this window to use for later.
Download your "Firmware" for your R4i. When you purchase your R4i, the manufacturer will provide you with directions on how to download your "Firmware" online. Choose the English version that relates to the R4i card that you have purchased. Wait for "Firmware" to download. The "Firmware" will download as an .Rar file.
Abstract the content in the Rar file. Copy the files onto the MicroSD card. Open the window for the MicroSD card that you minimised. Click the folder twice to open the Rar files contents. Highlight the contents to copy and paste them onto the MicroSD window. Wait for files to paste onto the MicroSD card. Your MicroSD card is now set up to be used with the R4i.
Download DS games. If the files are in an Rar format, open the Rar folder to abstract the game file that ends in ".nds." Copy and paste that file onto your MicroSD card window or drag the file onto the MicroSD card window. Do this for as many games as you want to place on the MicroSD card.
Remove the MicroSD reader from the USB slot and remove the MicroSD card. Slide the MicroSD card into its slot on the back of the R4i card.
Slide the R4i card into its slot on the Nintendo DSi and turn on the DSi console. A little R4i icon will appear on your screen with the words "R4i-SDHC" above the icon. Click on the icon.
Choose the game of your choice and start playing.