Hi Paul. I have to agree with the other comments but it still is a nice image. Don't be fooled M42 is one of the hardest targets in the sky and will keep most of us busy for our lifetimes trying to get it right. There are a few methods that can be used to retain detail in the tra whilst still maintaining the detail in the nebula.
1 HDR Merge in photoshop.
2 Follow the details in the link AlexN posted.
3 A program called EasyHDR which is used a lot by Avondonk on this forum.
4 Then this link which is one of Jerry Lodrigus' methods and by far the easiest to try. Much easier than his other method posted by Alex.
http://www.astropix.com/HTML/J_DIGIT/COMP2.HTM
Keep at it like the rest of us. Time and perseverence brings results.
Nice image just the same.