Magnus Manske wrote:
You can mow add to Encarta articles online. After a review by the M$ staff, your edit may be added to the Encarta.
They even specifically denounce Wikipedia's factual accuracy:
Encarta is different from open-content encyclopedias found elsewhere on the Web that post users' changes immediately. To ensure the greatest possible accuracy, all suggested changes to Encarta undergo fact-checking before being posted. As an encyclopedia, accuracy is one of our hallmarks, and even articles prepared by our own editors are fact-checked before being included.
They also have a page "About Editing Articles in Encarta" which essentially sums up many of our policies such as NPOV and avoiding peacock/weasel terms.