If a folder in Windows 7 suddenly has a Lock on the folder icon.Here are some simple steps you can use to remove the lock iconTo remove the Lock icon, here are the steps that I used:
1. Right click the folder and choose Properties.
2. Go to Security tab and click Edit.
3. Under Permissions for Shared Folder window, click on the Add button.
4. Type in “Authenticated Users” in the field and click Ok.
5. Click apply, Ok to close all remaining windows.
6. The Lock icon should be gone!!.