Note: These titles will work in WMM 2.1 (XP) and WMM 6.0 (Vista/Win7). I've provided XML for both versions in the installers.
Here's a sample video to help you visualize the titles.
There are two installers depending on whether you are running on a 32-bit or 64-bit version of Windows. The installer will put the necessary files into, C:\Program Files\Movie Maker\Shared.
Go to 'Tools' > 'Titles and Credits' > 'Title on the selected clip'.
Type your text in the first box.
Click on 'change the title animation'.
Under your list of one line titles, pick the desired variant:
As with other titles, you can change the font, background color and other styling attributes. Finally, click 'Done'.
Adjust the title duration by shrinking/stretching the rectangle on the Title Overlay track.