I've been a partner not for a couple of years, the best deal I got was a Free copy of XP.
. M$ gave it to me at the XP system builder roadshow. Sweet. I always jump on these promos when they come up, Great way to get cheap personal copies. Just remember, the EULA for these copies is not transferrable. Also, dont be supprised if M$ call you to survey your company on it's production. I get a call once a year at renewal time to see how many copies of the OS I have sold for the year etc...