Why Does 608MB Mpeg file Appear as 121MB When Burnt

[Ape]

Hi,

I'm using Nero 5 to burn an MPEG file for a VCD. The file is 608 MB when I look at it on my PC. When it has been burnt onto CD, it is only 121MB.

How can this be so. Am I losing quality when I burn (Is there some setting in Nero).

Thanks,

Ape