1.Find mp3 song u wanna set as default MW2 background music
2.Rename it to "hz_t_oilrig_themestealth_v1"
3.Go to X:\Program Files\Steam\steamapps\common\call of duty modern warfare 2\main
4.Find file named iw_20.iwd and open it with Winrar/7-zip/...
5.In iwd archive go to iw_20.iwd\sound\music\
6.Replace orginal mp3 file in iw_20.iwd\sound\music\ with custom mp3 file (renamed)
7.Start MW2
[YOUTUBE]<object width="480" height="385"><param name="movie" value="https://www.youtube.com/v/B0jpd3cZnYc&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="https://www.youtube.com/v/B0jpd3cZnYc&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>[/YOUTUBE]