This tutorial is for mappers that want a song from video games, mainly consoles like PS2, GCN/Wii, Xbox 360, etc. It can include portable and older consoles (See SNES, PS1, PSP, N64, NDS, etc.) but it requires more things to get the music from them.
This tutorial will require several things. These will be listed in case so if you don't have them you can download or seek more information about them:
Inside of our music folder. Look that we are on the sound/stream folder.
First download and install the required applications in your computer (If you don't have done yet). Once you have them installed, open foobar2000 and open Windows Explorer to the music folder of your extracted backup. Note: The name of the folder can vary depending of the game. The usual names for the music folder are stream, sound, bgm, music. Note 2: Some games use a different extension or not extension at all due to engine limitations/programmer whines/whatever reason. Usually a Google search can give you information about those specific games.
Once you are in the game's music folder, is time to load the songs to foobar2000. To do so, select all files in the folder and drag them to foobar's window. Once the songs are loaded, listen each one until you get to the desired song. In this tutorial, we're seeking for Chapter 3 Boss Battle Theme (We can't spoil the real name for those who are still playing the game :p) so our file is btl_gns1_32k.stm. Feel free to listen the song if you want.
Once you have the song that you are converting, right-click the song in the playlist, select Convert and then the ... option. This will bring you to a dialog so you can select how the conversion will be done.
This list will give you the correct setup for converting them to osu!:
Note: If you haven't converted to MP3 in foobar2000 before, the converter will ask you to locate lame.exe. Navigate to the folder where you have extracted lame.exe and select the file.
Once you have your options set, click the Save button and when it asks to overwrite the preset, click in Save as new. Give it a name so you can convert future songs quickly. Once you are ready to convert, click on the Convert button so the conversion process can start. Once it's finished, search the folder for the resulting file. In our case, the file is btl_gns1_32k.mp3.
Once we have our converted file, load it in foobar2000 or in your prefered music player to check if the song converted to your linking, if not, review the conversion settings until you have an appropriate file. Once the file is ready, drag it into osu!'s window, fill in the tags and start mapping!