Game Boy Advance users will be familiar with the cartridges used to play games on their device. But what if you want to load your own software onto your GBA? That's where flash cards come in. Flash cards (also known as flash cartridges or flash carts) can be written with any GBA-compatible software that you specify. Creating a usable flash card will require you to have a blank, writable flash card and a USB adaptor for your PC.
Insert your blank flash card into the USB adaptor.
Plug the adaptor into your computer. Your computer should detect the card automatically and open a window showing all the files that are stored on it (at this point, no files will be visible). Leave this window open.
Click and drag all relevant software files into the flash card window. It may take a few minutes for this software to be written to the flash card.
Unplug the flash card from the adaptor. Insert it into your GBA. Turn the GBA on. The software on the flash card should run automatically.
While you can use custom flash cards for home brew games, using them to load pirated games onto your GBA is in violation of copyright law.