See
http://word.mvps.org/faqs/formatting...ectionInfo.htm.
To find and delete section breaks in the source document: In the Find and Replace dialog box (Ctrl+H), specify ^b for "Find what" and leave the "Replace with" box empty. Click the Replace All button.
If you want to use the Insert File dialog box, here's how to display it in Word 2007/2010: On the Insert tab, click the arrow on the Object button, and then click Text from File.