For years, Microsoft has raked in money with Office. It's been THE leading revenue generator for ages with $4.4 billion in 3Q 2009. Office and related business products bring in more money than their Server/OS division. However, that number is trending down to the tune of almost 500 million from the same time last year.
Maybe it's just the recession. Maybe it was the Vista impact. However, the decline is noticeable.
Source: MS Annual Reports and Earnings Releases