窓辺ななみ(Madobe Nanami) is a kind of OS-tan based off Microsoft Windows 7. Her name is a wordplay; 窓辺 (madobe) meaning by the window, and ななみ (nanami) being a name derived from a pronunciation of seven in Japanese.
She was first introduced on September 25th, 2009 as the promotional character upon the release of Windows 7 in Japan. However, in reality she is not the official character for Microsoft. Her actual title was "自作PC応援キャラクター (self-made computer helper)." Yet, she had a very close relationship with Microsoft that she was "official" without the paper works.
The production was taken on by Windows 7 Mania Office , a group associated with Microsoft and sales agencies for Windows 7. The design was produced by an artist Wakaba and the voices of character were done by singer-songwriter and voice actor, Mizuki Nana.
Without a doubt, her basic model comes from OS-tan. However in this case, she is closer to human with a Windows 7 themed costume.
Special wallpapers and system voices were handed out along with other goods as a bonus in PC parts retail shops to those who pre-ordered Windows 7.
In March of 2010, Nanami's character song "七色ジェネレータ(Nanairo generator)" was handed out on CD as a bonus.
In May 2010, her Anime commercial started to appear in stores of Akihabara.