Re: How to unlock files.
These folders either have locks on them that need to be cleared. Try getting info on each folder and click on the General disclosure triangle and see if the "Locked" checkbox is checked. If so, uncheck it. See if it works then.
If you would rather just clear all locks on the entire disk in one fell swoop, copy and paste this into a terminal window:
chflags -R nouchg "/Volumes/EXT DISK"
Note: This command will only work if you have already checked the "Ignore ownership on volume" as I specified earlier