Sharing violation?

Recently some files burned to CDRW gave message certain files could not be copied due to sharing violation. These files were read only, and trying to change that attribute failed. Then files were copied to USB 2.0 thumb drive, and attribute could be changed but still gave “File could not be copied due to sharing violation” message. Finally I booted to safe mode and copied files from thumb drive with no problem. Has anybody an explanation for this kind of problem, and is there a way to copy such files when booted normally?

What mode and FS does that CD-RW have and how were it recorded?

Files were burned to CDRW disc using Nero to create data CD which I believe is why attribute couldn’t be changed because I think Windows alone isn’t able to do that. If it had been done using InCD or other packet writing program, then attribute could likely be changed. However, I no longer use packet writing because of many problems using it. The attribute change issue doesn’t concern me as much as why safe mode was necessary to copy files even after attribute change.