You have to make sure you have enough resources to reencode the software during the rendering stage. Make sure that MovieFactory is the only software running at the time. Disable any screen saver or anti-virus software running in the background.
You'll also have to consider the formats of the video clips that you used for the dvd project. Compression formats with high level compression like MPEG4 (DivX, XviD, MP4), WMV, RM, etc. will take a longer time to render and will use up more of your system resources so it is not advisable to work with them. The use of RAW AVI, MPEG1 (for VCD) and MPEG2 (for DVD) is recomended.
