Microsoft and Viacom are getting together for a large ad deal, in which MS will be serving ads from TV and movie content licensed from Viacom on sites they own. In particular, Viacom is buying the right to use Microsoft's "Atlas" technology to push ads, and Microsoft in turn will be able to put content from Viacom up on their sites and services.
Those services include things like Xbox Live, but not searching. The deal is likely the final blow in the relationship between Viacom and Google. Formerly, Viacom used DoubleClick to dispense advertisements online. That might soon become a conflict of interests, however, as Viacom also has a $1 Billion lawsuit pending against Google and Google is still trying to get their DoubleClick acquisition approved worldwide.