Thanks to all for your replies! Here are the results.
Fully uninstalling and then reinstalling NERO did not fix the issue, unfortunately
Loading NeroBurnrights and running the Nero registry checker did not fix the issue.
Good link, however...thanks burninfool!
Looking at the drive burn properties in My Computer showed that neither the TDK nor the HP DVD were checked!
...thank you again inertia.
Thus far, nothing seemed to help, but inertia's message gave me some insight into looking at the native XP burning engine (as the Nero error message should have...duhh)
First shot was turning off all Windows services using msconfig. (all startups were also turned off)
Nero starts up normally!
Turn on the services; Nero fails.
Looked at the individual services and saw that IMAPI was checked...unchecked, rebooted and Nero started normally.
! Rechecked, rebooted and Nero failed.
Looked at each of the individual services using the administrative utility and found that the Microsoft IMAPI service, though stopped and set to start manually, had been enabled, most likely due to the Roxio installation. DISABLED the IMAPI service, rebooted and lo and behold, Nero works!
I could only get Nero to start if I fully disabled the IMAPI service...stopping it or setting to manual start would prevent Nero from running.
My conclusion is that the Roxio installation checked to see if the IMAPI service was running and even if not, set the service to manually start (but left it enabled). Nero checks to see if the service is enabled (rather than running) and if so, gives its error message.
Long process, but now it seems as if Nero and Roxio will somewhat peacefully coexist. I generally don't use UDF type packet writing, so I've disabled the Roxio drag-to-disk facilities by turning off the following start-ups (using msconfig though I could delete the registry keys).
I've also turned off the following HP start-ups so that I don't get their notifications when I insert a CD or DVD:
If anybody sees any issues with tuning off these start-up items, please let me know. Thanks again to all!