Microsoft has decided to change their Logo after 25 long years. The new logo includes a multicolored symbol that's typically found on the company's Windows products. They are prepared to change the logo in Windows 8, Windows Phone 8 OS, Surface Tablet, XBox and in every other windows products.
The logo has two components: the logotype and the symbol. For the logotype, they are using the Segoe font which is the same font used in every product as well as in marketing communications.
Source : Official Microsoft Blog