You likely have some stray video clips floating out on your timeline that is artificially inflating the size of your project.
In Timeline mode, press the \ key (above the Return) key. This will display your entire project on the timeline. How long is it?
If it's longer that you want it to be, drag around the timeline in the "empty" area beyond your movie to snag any stray clips and then press your Delete key. Then press the \ key again and see if your timeline resizes properly.
BTW, an MPEG may not be the best format for you to play on your computer. Much depends on your project's settings, how you plan to deliver your project to your audience and what operating system you're using.
Thank you Steve. You were correct. I had some random title sequences hidden well down in the timeline. Thanks for your help.
For others, who might happen upon this thread, perhaps this ARTICLE will give them some clues, as to what has happened, and how to see the issue.
Good luck, and thanks for reporting your success.