With Jean-Marie Messier no longer at its helm, Vivendi Universal ( V) Wednesday began the process of dismantling the sprawling media empire he tried to build over two years. The French-American conglomerate announced it will sell its Houghton Mifflin publishing house as part of a $10 billion divestiture aimed at reducing its crippling corporate debt. Vivendi also announced a crushing $12 billion second-quarter loss, primarily reflecting an $11 billion writedown of goodwill and more than $3 billion in reserves. The company did manage to post a 13% rise in the first half, about double what analysts were forecasting. Under a plan approved Tuesday, Vivendi plans to sell half of the planned $10 billion in assets over the next nine months. Houghton Mifflin was acquired in 2001 for about $1.7 billion. The company's shares were trading down about 2.5% at $14.95 in the Instinet premarket session.