WinDVD stops and restart reading CD

> My Toshiba Satellite A-30 reads some Video-DVD win WinDVD 4.0 with
> interruptions: it suddenly stops showing the film (sometimes also the
> sound, but not always) and then continues, sometimes first with a
> staccato of pictures, and then contineously.
>
> The selection of the region should be ok: the DVD is region 2, and
> WinDVD is configured for region 2.
>
> Where can I find info on how to remedy this akward situation ? Is this a
> question of the speed of the DVD-reader? A question of the configuration
> of the program?
>
> I use Win XP SP1.
>
> Thanks,
> Frank