I have seen many shareware software on the internet which can convert from various video formats to one another. For instance, Advanced X Video Converter which is also conversion software. It can convert from DAT (VCD) to MPEG. But the other day, I just renamed a .dat movie file to .mpg and it works fine. So why do i need to use a software to convert when all i do is rename the file? Are these software really doing something that is worth buying it?