Unfortunately, I have tried all the updates I could find on the Nero website. When I try to install InCD 4.x I get a "To qualify for an InCD upgrade you must have a licensed version of Nero or InCD installed on your computer" message. I've tried it both with my old InCD installed and then again with it uninstalled, with my old 5.5 Nero installed and then again with Nero updated as far as I can go with 5.x. Same message every time.
Apararently my TDK-specific version of Nero isn't considered a "licensed" copy(??). And the 4.x InCD upgrade/update is the only one available on Nero's site. There are archived updates for Nero, but apparently not for InCD.
Maybe InCD requires having Nero 6.x, but the website says I cannot update Nero from version 5.x to 6.x (without paying) - it's considered a version "upgrade" as opposed to an "update".
One thing I've thought of - I have a number of XP Services turned off, but I did restart every service I could think of that I could think of that had even a remote connection to CD/disk/storage functions. Nothing seemed to matter. Is there one I'm missing?