A lock file (*.lck) is created every time you open a document. This lock file prevents others from changing the file while you work in it. A lock file is in the same folder as the original document and is removed when you close the document. You can turn off file locking.
If you try to open a document that’s already open and if you have write permission to the document, a dialog box displays the name of the document, who opened it last and when, and the computer on which it is open. You sometimes see this dialog box after a system crash when you open a document you were last using.
Open the file and do one of the following:
If you want to look at the file but not change it, click Open For Viewing Only, and then click Continue. The document appears in View Only format.
If you want to edit a copy of the file, click Open Copy For Editing, and then click Continue. A copy of the file is opened and when you save this file you are prompted to provide a new filename.
If you want to edit the file and you know that no one else is using it, click Reset Lock And Open, and then click Continue. Use this option after a system crash to edit a document that was open at the time of the crash.