I shall be wrong. I took some time and did some research. I've found that you can add quicktime to the background. I was curious on this. So, here is the deal. By what I've been reading. Only a MAC OS will do this.

I wish windows did something like this. But since Apple and Mac go together, Quicktime doesn't act goofy on Mac OS. This is the only reason your able to make a quicktime movie your background on your desktop. And I bet you just want the link I have so far.
Hmm, should I give it to you?
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Here it is, I thought about it and I decided you can have what I've found so far.
>>http://www.macrabbit.com/deskshadeplus/ <<
One other thing. For those windows people. I did find something but you have to really mess with some files to get windows to do it. Until I find a good instruction on that, I won't post it. If I find anymore I'll post them.