Claudia Madobe

Claudia Madobe is the official OS-tan for Windows Azure, Microsoft's cloud computing service and operating system. She is one of the few 'tans to be created by Microsoft themselves, following the Silverlight-tans and predating the 8-tans. She currently is the mascot for Windows Azure in Japan.

She has a Facebook and Twitter account as well.

(Source: OS-tan Wiki)