Mac "The operation can't be completed because the item xxx is in use"

This error is in all Mac OS X Versions up to 10.7

Delete something in a Network Drive

It happens then I want to delete something from the network drive.
It turned out that the program Quicklook use the file.
This is the case then you use the finder in the cover view mode.
The file, in my case a picture,  is viewed with Quicklook.
Use the normal list mode and you can delete normally.

How to find out which program is using your file

Open the Terminal

lsof -l +L -R -V | grep "Name-of-the-file"

alternativelly you can use

lsof -l +L -R -V | grep /Volumes

in the case your file is on the network drive

Stopp using
Killall Finder

to stopp  Finder  to use the file

Remove with Terminal

sudo rm -rf "path-and-name-of-the-file"

drag and drop the file to the Terminal windows you get the correct path and name!

If you get this error deleting the trash

Simple solution

Right click the trash and use "Secure Empty Trash"
You find this also in the Finder, menue Finder, Secure Empty Trash