I recently bought a brand new Dell Dimension 8400, Pentium 4, 3.4GHz,
1.00GB RAM, and have been trying to use my Sonic DVD/CD Burner program
to burn ISO files onto a data disc. however, it will not recognize the
DVD-R cd's that i put into my computer as 'appendable discs'. i was
wondering if anyone out there knows of free, downloadable software
which can convert my ISO files into standard AVI/MPEG files, which i
can then process into burned DVD's... rather than data discs.
if you need any more information, feel free to email me at theoverworked@yahoo.com

Well I know of no free program isobuster will do what you want. You
just open up the iso with the program then you open up the mpg file
that will aprear on the right and open it then you will see a .dat
file right click and select extract mpg it should be the second
option. and once you have extracted it then just rename it to avi.

http://www.smart-projects.net/isobuster/

DVDx will extract and covert a DVD to either an MPEG (VCD,SVCD,etc) or
an AVI (DIVX etc) for more information on it, check out it's webpage:
http://www.labdv.com/dvdx/

It's free, but you have to pay to download it from their site (they
want to cover their bandwidth costs) but you can download it for free
from: http://www.digital-digest.com/dvd/downloads/showsoftware_dvdx_146.html

The program is aimed at novices, essentially a wizard type interface. 
Then you can just use NERO to create a 'proper' movie DVD.