split --bytes=1024m bigfile.iso small_file_
That command will split bigfile.iso into files that are 1024 MB in size (1GB) and name the various parts small_file_aa, small_file_ab, etc. You can specify b for bytes, k for Kilobytes and m for Megabytes to specify sizes.
To join the files back together on Linux:
cat small_file_* > joined_file.iso
If it was a video file and the file would not seek then VLC can fix the video index or even better use
mencoder -idx inputfile.avi outpufile.avi
to regenerate the avi index