Burning DVD - ULead Video Studio 7

[RJP1952]

When rendering the same 10 minute .WMV file (combo slide and video with audio) to DVD, I have had successes and failures. The successes appeare to show burn tracks on the inner portion of the disc, and work on my stand-alone DVD player as well as my dvd device on my PC. The failures appear to burn the entire disc, do not work on my dvd player but will run on my dvd drive on my pc. I believe I am doing the rendering using the same approach. I have had 2 successes and 2 fails and don't understand why. The process takes about 3 hours, which seems too long to me.

Working on a 1.4 Ghz machine, Windows XP pro op system, 512 MB ram

Any help would be appreciated