image filetype help...what burner?

[tarku]

ok...I have the image file for DDR4th mix for psx..and I cant rememeber what program it ctakes to burn it back to cd. I have nero..and well I know there image file is *.nrg... so what is *.cdi file?
this has been bugging me for a bit...what burner program is the image file *.cdi??

please help

ps I searched the forums already..I couldn't find anything