Picture not Filling the screen

[enfield250]

Hello!
I have been capturing some old VHS holiday videos, Using a USB device and Honestech VHS to DVD software.
the original aspect for the videos was 4 x 3.
The software saves the video as 720 x 576 mpeg.
I then load this into PRE9 and edit the footage, and save each edited part as PAL DVD Widescreen, SD 720 x 576.
When I look at each part on the monitor it fills the screen top to bottom with the expected black sides.
However, when I then join the parts together the picture is Letterbox in the centre, even though it is still 720 x 576.
Anyone got any idea what I'm doing wrong, please.
Cheers,

[DB83]

Simple.


Do not export as Widescreen.