Fitch rates Microsoft lower than S&P, Moody's

In a release late Thursday, Fitch assigned Microsoft an "AA+" rating for long-term debt. The software company has no long-term debt, but on Monday it announced that it would borrow $2 billion by issuing short-term commercial paper, an unprecedented move for the company.

Fitch assigned the commercial paper its highest short-term rating, "F1+."

Microsoft intends to use the money to return cash to shareholders through buybacks and a raised dividend, and Fitch said it expects the company to tap long-term credit markets for the same purpose.

Moody's Investors Service and Standard & Poor's Rating Services both assigned Microsoft's short-term and long-term debt their highest ratings.

Fitch said its long-term concerns are that Microsoft's business model could be challenged by free open-source software or software that's used via the Internet rather than being installed on the user's machine. Margins could come under pressure from growth in emerging markets, where prices are lower, or be affected by results at its console unit. Also, further legal and regulatory obstacles could arise for the company, which has faced multiple antitrust investigations.