This viral marketing is what corporate and political campaigns increasingly thrive on, and today it's mostly free.

WSJ: Andy Kessler: When Will Social Media Elect a President?

But if past Windows launches are any guide, Microsoft will help its cause by spending hundreds of millions of dollars on high-profile TV ads, viral whisper campaigns and "co-marketing" money for its PC hardware partners and the resellers who push Microsoft software to big corporations.

CNN: This is the year Microsoft fights back