How to author HD content???

[TheAdMan]

I need someone to school me on authoring DVD's in High Def.
I have a project that I would like to export to 1080 resolution, but have a few questions, any help is appreciated:

1)What Authoring programs support HD resolutions? (I have been using DVDlabpro for 720x480 up to this point.)

2)What is the difference between HD-DVD and DVD-9? Can I burn HD-DVD with regular DVD-RW drive?

3)You can burn HD content on regular DVD as long as file size is below 4.7GB - Y or N?

4)What encoders support HD resolutions?

thnx again.

[Semaphoric]

re #3:

I've read that you can indeed do this, but that the resulting discs can only be played in HD on HD-DVD players, not Blu-ray.