Note: This title will work in WMM 2.1 (XP) and WMM 6.0 (Vista/Win7). I've provided XML for both versions in the installers.
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, find the new animation:
As with other titles, you can change the font and other styling attributes. For the best results, pick a big, bold font like Arial Black. Note: the color you choose for the font will actually be the color of the background, since the video and text are reversed.
Finally, click 'Done'.
A couple additional things you might want to do. If you want the title to take longer, stretch it to the right. I added the 'Fade In from White' effect to the video so that the text would start white.
Note: The latest versions of Movie Maker do not allow customization, so this does require a classic version of Windows Movie Maker. If you are on Windows 7, you can install WMM 6.0.