Download NFSU Music Importer
Download the "Music Importer" and in the zip file you will find the "music importer" and an "MCO Music Importer" (an ASF converter) to convert your mp3,wav,wmv,etc. files into .aif files so you can import it with the music importer.
Run the MCO Music Importer and browse your favorite .mp3, .wav or .aif song (in the "Convert File" bar)
Choose a destination folder (any folder, for example "My Documents")
Click "Import" to convert your file to .asf format.
Run the NFSU Music Importer.The program scans your drive for NFSU songs.
Than you have to select an existing song title and click "Import ASF Music Track".
Now you browse for the convertet asf file (My Documents).The importer will replace the original song that you have selcted with the convertet asf file.
ATTENTION: The original song will be completely replaced by the converted file.This can not be undone.The original track will be comletely lost.The song title/artist/producer ingame will not change as it is hardcoded into the game executable.
Hope this helps B)