Utopia wont work
 

i used nero 7 to burn the Utopia.cdi file to a CD-R but it wont read in my dreamcast, could someone please help me, I cant get it to work in any of my 4 dreamcasts

Using anything but DiscJuggler to burn the Utopia boot disc has always failed in my experience. Thankfully, DiscJuggler is still being produced, and you can find a demo version here.

(In general, Nero is insufficient for duplicating pretty much any kind of copy protection - be it for a PC or a console - as it is rather aimed to be a full CD/DVD/audio/video conversion/burning/imaging facility. So, yes, you need a software specialized at copying protected disks instead.)

two more questions what version of utopia should i use? and Is there any other file i need to put on the disc other than utopia.cdi?

That file is a CD image. Burn the image itself; don't put the image as a file into an empty CD complication and burn that!