<sarcasm>Everyone enjoys seeing Windows messages like the following:</sarcasm>
You can’t delete files in Windows when their file handle is still open in the operating system. This can still occur even after you closed the document and the application that was used to display it.
One solution is to reboot the computer which may release the file handles, but this doesn’t always work. Unlocker is a system tray application for Windows that can force file handles to close and delete processes. Unfortunately, it won’t delete locks over networks, but there are other ways to do it manually.
The application is free and it uses very little memory when running. You don’t need to run it all the time, though. I just use it when I have file problems and then close the application afterwards. This is a must have application for Windows users.