Invalid Disc With nero Express 3

Hi Everybody,

I'm trying to burn a number of music videos (mpg) 21 in total with nero express 3, everything seems to be fine apart from two things

It takes over 3 hours to encode etc

Everytime i put the finished disc into any dvd player it says invalid disc.

I've used this prog to burn a couple of movies with no problems at all

Can anyone help or suggest a better prog?

Many thanks!