if it's a movie, i'm using DVDFab Platinum for this, it allows to span movies over multiple (usually 2) DVDs.
load the ISO, choose Split from the DVD to DVD menu and let it work its magic. :)
of course it doesn't stop there, DVDFab can 'shrink' the entire DVD to make it fit on a normal (DVD5) or DL DVD (DVD9) using compression, or you can remove trailers, unwanted audio tracks, bonus material, etc. with a few mouse clicks to make it fit.
DVDFab Platinum is shareware, try before you buy.
Edit: so it's a software DVD image and we don't know it's origin or content. without knowing the details, i assume this is some measure of copy protection, so i suggest this:
simply mount the ISO with WinCDEmu as a 'virtual DVD drive' and quit wasting precious blank DVDs :)
for portability, copy the ISO to any external device big enough, a 16 GB SDHC card for instance is much smaller in size than a DVD. :) if you want to burn it onto DVD for storage purposes, just compress the image with 7-Zip and split the archive into DVD-sized chunks.
WinCDEmu and 7-Zip are free open source programs.