Any number of factors.
* Your operating system and the speed of your processor.
* The format, resolution and source of your original video (especially if it's not camcorder video)
* The size of the photos you're using in your project (especially if you haven't optimized them to no larger than 1000x750 pixels in size)
* The number of effects, graphics and titles in your video.
* The length of your video.
90 minutes is a very long video. Only about 70-80 minutes of video can fit on a DVD at full resolution. So, in addition to all of the other processing the program is doing, it is also adjusting bit rates and compressing your video so that it will fit on a disc.
Perfect, now how I burn the same video in two or three disck, or I have to edit it over again?
Thank you for your cooperation.
What did you do that allowed you to burn a disc, Victoro?