file unexpectedly big..
 

Im hoping theres a really simple answer to this but some how i doubt!

I use nero express 6 to make vcd's. ive burnt an mpeg (764mb) to cd-r perfectly ok but when i tried to burn an avi file (483.4mb), it seemed to double in size when i added it to be burnt and told me it wouldnt fit on a 700mb disk!

I really dont understand why this has happened. the file encoded fine. is it because its an avi file?

can anyone enlighten me?