DVD Burning 1 DVD to 2 DVDs Nero 7 StartSmart Essentials

Hello,
I am trying to make 1 DVD to 2 DVDs.
There are 2 IFO and 2 BUP and 1-2-3-4-5 of the video.
The first DVD using both IFO and BUP plus 1-2-3 have been burned and work on a DVD player and Windows Media Player just great.
But the second DVD with both IFO and BUP plus 4-5 only play on the DVD player, not Windows Media Player.
Why is this? What am I doing wrong?
Thank you
Tootsiesmom

to math good

When you use IFO and BUP you have to create same for the first one also you need for second if you convert you gave order to seperate in to dvd-s i use winavi try that one it will help you.