I have numerous video files on my hard drive which are "windows media audio/video file" format. When i encode them to mpeg3 so i can put them on a DVD they increase to a huge size

. eg a 75 meg "windows media audio/video file" becones a 593 meg mpeg 3 file. Is there any way i can keep the encoded file close to the same size as the original???.
BTW i'm using "Sonic My DVD" to encode.
Any help would be appreciated