Are you sure the iso file is all ~700 MB?
There's some other burning apps you could try, here's at least howto's: http://members.home.nl/lsnoek/iso.htm
You could just google for trial version for places like: http://www.snapfiles.com/shareware/gmm/swcdburn.html
I seem to remember people liking alcohol for burning images: http://www.alcohol-soft.com/