The file that looks like this is the editable file you make changes with.  It is not one you would send to others, post on the web, burn do disc, etc.  When you have your video like you want it you need to convert it to a .mov (Quicktime) file that others can use. 

 

The steps are:

1.  Make sure your original iMovie file is saved one last time.

2.  With it open go to "File" and choose either Share or Export depending on which version of iMovie you have.

3.  Select the Quicktime feature and not Camera, iDVD, etc.

4.  Now you have to choose which size you want to export it as.  Web, Streaming, and Email are very small and hard to see.  You should choose CD which will give you one that you can see easily and is small enough to fit on an iPod, thumbdrive, network.....etc.  Full Quality or DV is for burning to DVD's to show in a DVD player.  This choice will give you a file too large to move easily.

5.  Next it will ask you to give it a name and it will probably default to the Movies folder of your computer.  You can save it as whatever you want and put it where you want just pay attention to where it is going.  It will take a while to do the conversion/compression from the original iMovie file to the final .mov Quicktime file.

If you find a mistake in your final .mov file then you'll have to go back to the iMovie file and fix the mistake then go back and export/share it again to show the changes you made.