Remco - 'skins' get put in Gamedata folder as part of the mod - see this thread for the skinpack and a fix:
http://www.racedepartment.com/nations-grand-prix/40109-ngp-s3-skinpack-must-download.html
http://www.racedepartment.com/nations-grand-prix/40109-ngp-s3-skinpack-must-download.html