hi catt, welcome to the site!
this thread might be useful: https://www.donation...dex.php?topic=1263.0
here's some general advice, though others are welcome to correct me:
you should probably avoid setting things to any priority above normal unless you REALLLLY want them to own your pc
in general, setting something like nero to Ignore would be your best bet, to make sure it doesnt get lowered.
however, if you frequently run other processor intensive stuff at the same time as using nero, or you experience issues with nero not being able to keep up on a slow machine due to some other process popping up and using your cpu, then you could try setting priority to high.
but like i said, it's almost always sufficient to just set an app to ignore if you ever find process tame lowering it and you don't want it to.