There you are, minding your own business trying to delete a file, but your system says NO! Now maybe it's because your word processing software has the file open and you're writing to it (duh) so your computer is keeping you from shooting yourself in the foot. Okay, that's good.
But maybe it's not so clean. Maybe you've closed all of your apps and you still can't delete that file. Now you have to wonder whether whether you've got some ill-mannered piece of malware that's trying to do bad things to you, or if it's just Windows up to some of its old tricks. Either way, you still want to get rid of that file.
LockHunter may be the tool for you. Find out which process is locking your file, and then decide what you're going to do about it: delete the file, kill the process, or even delete the app that spawned that process. And just in case, you can delete into the Recycle Bin so that if you need to go back and resurrect your deleted file, you can do so.
LockHunter is a free Windows application, and will run under Windows 2000 and later. It's still technically in Beta, so you'll want to be careful about using it for any mission-critical applications.