To start with, hold down the Option and Shift keys while emptying the Trash; this sometimes enables locked files and folders to be deleted.
If that doesn't work, double-click on the LaCie drive in the Finder, and then choose Go to Folder from the Finder's Go menu. Enter .Trashes/501/ as the folder's path; if the Finder tells you that the folder can't be found, increment the number by 1, and keep going until you find a number that works. If you've reached 510 without finding a working number, open the Terminal in your /Applications/Utilities/ folder and enter 'id -u' without the quote marks. The output of this command is the number you need.
Once you've opened the folder, open the Terminal and enter 'chflags -R nouchg' without the quote marks, follow it with a space, and then drag the little icon at the top of the Finder window which contains the folder you opened into the Terminal window. Press Enter and empty the Trash again.
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