Possibility of a bad disk? Try a different disk and or brand to be certain. What about going back to a previous version of Nero? What is the drive type and how is it connected? Master, slave, primary, secondary, etc... Windows XP Pro Sp2 or Sp1, etc...?
Check task manager to see what program may be causing Nero to use 100% cpu. 100% cpu usage typically causes freeze related problems. Sometimes if a particular program hasn't been completely removed, pieces of it may linger in the background and disrupt legitimate programs in use (Nero in this case) and cause 100% cpu usage problems. Windows explorer is typically affected and causes itself and other programs to use 100% cpu. Try uninstalling programs other than Nero that you may have suspicious reasons to do so if they have behaved badly before in the past. This is a judgement call. Have you installed spyware scanners before? Try running scans for spyware as well.
Heat is always a concern. But, in most cases it rarely causes programs to free in my experience. If heat was really involved in your case, than the pc would most likely shut down or keep rebooting itself or even smell like burnt metal and plastic.
I personally think that you should focus your attention to either a bad disk or program conflict (programs that have been removed in the past that may still be in your system registry, bad shortcuts, missing dlls, etc...). Run a good spyware program and Registry program like JV16 PowerTools or Registry Healer, etc... when installing and removing programs to minimize lingering dlls, bad shortcuts, bad registries, and other forms of fragmented data that may try to attach themselves to legimate programs in use, i.e, Nero in your case. Other members may recommend other alternative programs to clean out your registry and system files. Good luck for now.