Scanreg /restore doesn't restore all of Windows, only the registry. Everything messed up, corrupted or rotten elsewhere (say, damaged or missing files in \windows\system) is unchanged.
The best way to prevent this kind of thing to happen is to make a 'snapshot' (copy, backup, whatever you want to call it) of the whole windows folder when it's in a working condition, either regularly or before doing updates. With some preparations this takes less then 10 minutes, which I consider a good investment of my time. A very good alternative is buying the Goback program.
Anyway, the fileinfo tool in the resource kit (on your Win 98 cd) tells that the dll is part of Windows. You can use SFC to extract it from the cd. Even if you had specified the error message it might have been impossible to say if this would help, and as you have decided to keep it to yourself that's even more so. But it wouldn't make the situation worse, I think.
Fileinfo also tells you that the vxd is not part of Windows. Presumably it came with 1 or more of the programs you tried to install, but which didn't work, or didn't work satisfactory. If the user manual or readme.txt (do read those files!) says they don't work with Windows 98, it's quite possible they mess things up beyond easy uninstall or even beyond easy repair. Especially if you choose to install the next and the next without proper uninstalling in between.
My best bet would be to remove the mention of vxd from the registry (it has a place where all vxd's to be loaded are listed) with regedit. This should take away the error message. Then uninstall (with Control Panel Add Remove, of uninstall links installed in Start/Programs) everything you can find regarding cd-writer programs. Some manual cleaning of the registry afterwards might be needed.
Then reinstall Nero and cross your fingers. You might very well end up with a format/reinstall. Everything else is pure luck, I'm inclined to say.
I do hope Bob offers some better advice, if you come up with the exact error messages. But I'm a bit pessimistic about it, to be frank.