4.4. Protect a File by Making It Read-Only
You can prevent other people from making changes to an important file by designating the file as read-only.
Much day-to-day work in Windows 7 is required but not terribly important. Most memos, letters, and notes are run-of-the-mill and do not require extra security. Occasionally, however, you may create or work with a file that is important. It could be a carefully crafted letter, a memo detailing important company strategy, or a collection of hard-won brainstorming notes. Whatever the content, such a file requires extra protection to ensure that you do not lose your work.
You can set advanced file permissions that can prevent a document from being changed or even deleted (see "Protect a File or Folder ...