Sometimes, files on the Mac cannot be deleted, moved or renamed. This can be caused by insufficient access rights, or because some processes are still using these files.
Unfortunately, the Mac OS X Finder doesn't tell the user which processes exactly are causing the lock. Also, these processes are often running hidden in the background - so they can't even be quit using the Dock.
Here, Lock-UnMatic comes into play. Simply drag and drop the affected files onto the application-icon (or into the application-window), and Lock-UnMatic shows you a nice overview of all blocking processes. It's also possible to kill these processes from within the application. More Info »
Lock-UnMatic is freeware and provided under the LGPL. The latest binary version can be downloaded in the Downloads-section, as well as the sourcecode. The application is multilingual (English and German).