Cheapest way to buy the next windows for 10 computers?

Catsrules

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Dec 6, 2008
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While windows 7 has been out, I have bought a few more computers, for my house, Laptop desktop, hometheater pc. Anyways I am managed to get all on my computer to have at least windows 7 home premium, and was wondering when the next new windows OS comes out, what is the cheapest way to upgrade. I think I will need around 10 licenses
Just get like 3 family packs of 3 licenses.
I have heard about tecnet and MSDN subscriptions, what is the story on those.
I am in school, and I hear you can get windows 7 for like $30, but I am guessing they will not let me get 10 copies for $30 each.
 

I read some where they you can only use that for testing stuff. Is that correct?
If So what qualifies as testing? I would use it for testing, learning how to use servers and domains stuff like that. But I would also use it for school papers and facebook, video games stuff like that.