Well, first open your picture up in MS paint.

Now click on the select tool. The select tool is the top most right tool on your tool bar. Once you have that tool drag a box around the section of the photo you want to enlarge and highlight.

Ok, now you want to copy that section using Ctrl+c or select copy from the edit menu. Once you have it copied you need to past it the copy back into the picture by using Ctrl+v or choosing past from the edit menu. You should now have a copy of the selection in the upper left hand portion of the photo. It should also be selected automatically after you past it.

You should now be able to click and drag the selected copy to any where on the picture.

Now, by moving the mouse pointer to the lowest most corner on the right hand side of the selection box. The mouse pointer should turn into too small arrows. Now click and hold down the left mouse button and drag the box out, re-size it. This will enlarge your picture.

Now simply use the line tool to draw straight lines around you selection and save your picture. Easy! :)