How can I open a file as read-only from Windows Explorer?

I had the same problem on Windows 7. The above answer doesn't work for Windows 7 because the interface for file associations has changed. The good news is that Open as Read-Only is now a simpler process.

SHIFT + Right-Click or hit F10 -> click Open as Read-Only

Open Windows Explorer.

Choose Folder Options from the View menu. (In some versions of Windows you choose Options from the View menu, or Folder Options from the Tools menu.) Windows displays the Folder Options (or just plain Options) dialog box.

Make sure the File Types tab is selected. (Click here to see a related figure.) In the list of Registered File Types, locate and select Microsoft Word Document. Click on the Edit button. Windows displays the Edit File Type dialog box. (Click here to see a related figure.)

Select the Open option in the Actions list.

Click on Advanced. The Edit File Type dialog box appears.

Click on Open in the Actions field.

Click on Edit. The Editing Action dialog box appears.

Select the contents of the Application Used to Perform Action box. (Click here to see a related figure.)

Press CTRL+C. This copies the contents of the Application Used to Perform Action box.

Click on Cancel.

Click the New button. Windows displays the New Action dialog box.

In the Action box, enter the name you want to appear in the shortcut menu. For instance, you could type Open Read-Only.

Position the insertion point in the Application Used to Perform Action box and press CTRL+V. The information you copied in step 8 is pasted into the box.

Select the Use DDE check box. The New Action dialog box expands.

In the DDE Message box, enter the following text: [FileOpen ("""%1"""),.ReadOnly]

In the Application box, enter this single word: WinWord.

In the Topic box, enter this single word: System.

Click Close or OK as necessary to dismiss all the dialog boxes.

Instead of Shift+Right-Click -> Open as Read Only, use Open in Protected View. Seems to do what's needed and prevents editing of the document. It should work for Word and Excel files.