You need to cut the MPEG2 file into two parts before burning. You can do this in TMPGenc, and I've written a guide at:
http://www.marcpeters.co.uk/tmpgenctools.html
If you have an AVI,I'd use TMPGenc to encode to SVCD compliant MPEG2, but do two encodes: one that encodes to halfway, and the other that encodes from halfway to the end. That way you get your two MPEG2 files which can be burnt seperately.