Let me provide a bit of background and hopefully this will help.
The latest version is Movie Maker 2012 which can be installed on Windows 7 or Windows 8. Only when it is in Windows 8 will you have the video stabilization option. So given that you are on Windows 7, that can't be the cause of your problem.
You have created a project using certain source files.I'm assuming while you are editing within Movie Maker, you are able to see a preview of your movie? But when you ask Movie Maker to create your final
movie using the instructions in your project file, that final movie file has no video in it, only black?
No. I can't see the PREVIEW of video in Movie Maker while editing. The video file gets uploaded for editing but plays only audio with a BLACK SCREEN.
Windows 7
Dell Inspiron 1525
Conversation with Dell Support:

Would running "nvidia driver 285.79" solve the 'black screen' problem on my Dell Laptop? Can only hear audio while using Windows Movie Maker... Cud edit d same files on another laptop. So, probably my softwares for running video r outdated. Just wondering
if d NVIDIA software is safe

Hi, thanks for reaching out. Please try updating the video drivers and check. Kindly let me know the version of movie maker. ^RS
This is a follow up. Let me know the status after updating the video drivers. ^RS

Downloaded 'Windows Movie Maker 2.6' as well. But its not detecting the video.
Movie maker is only detecting 'wmv' video file.

May I know what is the video file that is being played? ^RH

10-15 mins MOV files shot from iPhone 4S
The same files can be edited in another laptop (toshiba) but not on my Dell laptop.

May I know the type of file that you are trying to play and the model of the Dell laptop. ^RH

Video file of .MOV format [Dell Inspiron 1525]
A "Black Screen" can be seen instead of the video in the editing window...
Which software needs to be updated or installed?
http://www.dell.com/content/topics/segtopic.aspx/xp_mm?c=us&l=en&cs=19 …

Is it the same Movie maker that is installed on the other laptop? ^RH

Yes, both are of Windows but I don't know the version. Can I install one from CDs of Dell that I have or from sm website?
Do Dell Laptops have any other way of trimming (cutting) videos and substituting audio by inserting desired Music?
Eg in Dell Media Centre ?

You can purchase online 3rd party software's for the same. ^RS