With Nero, when you hit the write button, choose the burn tab when it comes up. Check the "Use Multiple Recorders", next window make sure your two recorders are highlighted. I also use this feature to switch between multiple burners. Using the same steps above, you just higlight one burner. It is a lot easier than going through "choose recorder" everytime.
To burn to multiple burners you will need to have scsi burners or your 2 ide burners should be on different channels. I do multiple burning with Nero all the time using Plexter scsi burners in an external case and it works flawlessly.
I have burned successfully using 2 different ide burners but it might be recommended to use matching burners. If you use 2 unmatched you can only burn at the highest speed of the slowest burner, if that wasn't already obvious.