See the second (Wiki) post under http://forums.slickdeals.net/showthread.php?sduid=0&t=1044322 for an explanation and tips. References how the eBay item must be a Buy It Now deal. Complicated, but worth it. You can get up to $2,500 per calendar year in cash back, up to 12 transactions, a limit of $200 cash back per transaction ($666.67 purchase price for maximum cash back).

Here's the Microsoft Live FAQs on the promo http://search.live.com/cashback/faq#faq0

--Norm