Isn’t it annoying when sometimes files won’t just get flushed along with everything else when you’re emptying the trash in OS X? It says that they are in use, even if you’re sure nothing is using it? One solution is to log out and then try again, but a quicker one is:
- Launch Terminal (/Applications/Utilities/Terminal.app)
- Type rm -r ~/.Trash/<filename>
TIP: use the tab key when you need to type the file name, as it will auto-complete the command for you. You can even start typing the first characters of the name and then press tab.
NB: Be careful with that command. If carelessly used can be harmful to the system.