how to compare 2 word file?

Solution 1:

Tutorial: Comparing Two Versions of a Word Document

Solution 2:

From How to Compare Word Documents Side by Side :

1. In Word, open the two documents you want to compare.
2. Choose Window.
3. Click "Compare Side by Side With" (it will also list the name of the second document, or simply say "Document2"). If you have more than two documents open, a dialog box will open allowing you to choose your second document.
4. You will see a "Compare Side by Side" toolbar. The "Synchronous Scrolling" will allow you to scroll through both documents at the same time.
5. If you want your documents to reset to their original positions, click the "Reset Window Position" button.
6. When you are finished comparing your documents, click "Close Side by Side".

Image for Word 2003: