Video compression

[Joyce Ranieri]

I'm sure this has been answered, but since I just joined the list, here 
goes:
I imported video from Christmas into iMovie. Then I played with it, 
added fade-ins, titles, etc. I "exported" it to iDVD. Then I tried to 
burn a DVD in Toast (newest version, for Mac OS X). The message is that 
the movie is too long for the DVD -- over 6 gigs and the DVD is 4.6.  
It's only about 30 minutes long and I don't want to "cut" the movie. 
How do I compress the video so it will fit?

Joyce