RTLNOOBIE

need some help on audio. first i have carpc and i used tape player for the sound but i hate the hazerling sound from the taper player. then i bought FM transmiter but i can hear every thing my computer do. i can hear the HD ticking and when i move window around i can hear the sound too. i wonder if it from the ground wire that i connect the carpc? anyone have idea what can i do to get smooth sound from FM transmiter?. the transmitter work good with my ipod but bat with th computer. and also i have build in HD soundcard and USB sound card they booth have the same sound that i mention about.

Thanks.