DeSmuME

Sometimes, people might get nostalgic about the time when the first Nintendo DS devices were released, along with the games they supported, and when this happens, they can try DeSmuME, a dedicated emulator app.
The application is an open-source software solution that runs out of the box, meaning that no installation is required. However, what you do need in order to start the emulation is a compatible ROM file (the program supports several types of formats, such as NDS, DS.GBA, ZIP, RAR, SRl, 7Z or GZ).
Once you loaded your files, DeSmuME starts emulating the experience from your game console, including the controls you need to be familiar with in order to fully enjoy the game (they differ with each game, so it is best to play around with the keyboard before starting a mission).
At the beginning, it might be a little bit difficult to get used to relying on your keyboard rather than an LCD screen with touchscreen capabilities, but the application offers other features in compensation, such as recording an AVI movie or a WAV track while playing or taking screenshots (then save them as BMP or PNG).
You can customize the layout of DeSmuME as you see fit, and you can start by specifying the type of border you would like between the two Nintendo DS screens, be it a narrow, a wide one or a non-existent one. You can also adjust the window size and rotation angle, as well as select a custom magnification filter.
The sounds can also be configured to your liking, along with microphone and firmware settings, yet it is best if these are adjusted by experts, so if you are a beginner it is best to leave them to their default values.
All in all, DeSmuME can help not only experienced users enjoy their preferred Nintendo DS games on their computers, but also the novices, as loading a ROM can be enough to start playing any game.