When I erase unused disk space I get an error with a long list of files that could not be processed. What am I doing wrong?
Nothing, the meaning of this error is to warn you that not all unused space on the drive could be overwritten. This is because the files on the list were loaded in memory and therefore, locked by the operating system and their cluster tips could not be erased. You can reduce the amount of locked files by closing as many applications as possible before erasing unused disk space. You can find more information about the cluster tips from the help file.