Copying to External Drive not working KDE
If your external drive is of the NTFS filesystem:
Sometimes a native linux install does not have the drivers to write to an external drive of the NTFS filesystem. When you try to copy to an external hard drive with dolphin in KDE; it will give you a message like: 'Could not copy to <hard drive>'.You will need to install the drivers.
#gentoo emerge sys-fs/ntf3g #debian aptitude install ntfs3g
Link to more details on the ntfs3g driver.
This article tells you what to do when: Copying to external drive not working KDE.