REF: Microsoft Office Word
Hi, am kevin from Mauritius, I really need your help. I am trying to open a word document
But it is preventing me and I got a message as such "this modification is not allowed because the selection is locked". Can you please help me , thanks a lot.

This modification is not allowed because the document is locked

"If you see this message at the bottom of the application window when you try to modify a document: "This modification is not allowed because the document is locked," the document is protected with an editing restriction of No changes (Read only) or Comments in Word 2003 (or a restriction of Comments in Word 2002 and Word 2000). The document author used the Protect Document features to restrict editing. Menu commands also might be unavailable, depending on the permissions that were granted to you by the document author."

" Note When you open a document that is protected by Information Rights Management (IRM) in Word 2003, you might have permission to view the document but not to change it. When you open the document, the Shared Workspace task pane opens by default on the right side of the application window. In the task pane, click View My Permissions to see your permissions."

http://office.microsoft.com/en-us/word/HA011406121033.aspx

There is also a link for "2007 Word Help" on the left margin of the above site.

I think your document is protected.
To make unprotect go to Tools -
Protection - check the submenu and find out the unprtect document option then click on that.
It will open your document. For the further help ask when problem comes.

You can unprotect it unless its been password protected. In that case you need to go to the author.