A family of Microsoft word processing software products for creating web, email, and print documents.
Here are a couple more possible fixes:
I keep getting files that I am working on locked for editing. Word only allows me to open them read-only
http://www.word.mvps.org/FAQs/AppErrors/LockedFiles.htm
“This modification is not allowed because the document is locked” error message when you modify a document
http://support.microsoft.com/kb/818852
File Locked – Read-Only
I had the same problem. In my case, after applying the latest updates (June 2015) word started locking files and all files i opened in Word were read only.
The problem was the Preview pane in Windows Explorer. When you click a word file, Winword.exe runs as a background process, locking the file. Even if you unselect the file, it is still running. Although before the update it worked correctly, somehow now is broken or a new ‘unknown to me’ setting has been added.