Problen in multisesion

help please, i burn a disc on nero 6 and wen i try to put anoter sesio it erases automatiqly the previos data. what should i do?

Welcome to the forum and CDFreaks, please explain what program of Nero 6 your are using for multissession? (Nero Burning ROM?, NeroVision?, NeroExpress?) and what writer are you using?.