HOW DO I STOP NEROVISION CONVERT BAC 2 MPEG2

[Hacker_Girl]

i TRYING TO BURN MPEG1 ONTO A DVD-R, but nero keeps convert the file to mpeg 2 compliant which defeats the object of me re-ecoding them to mpeg1 in order to fit more onto the disc...how should I go about this.....please help...thanks!