In case you’re interested/forgot/etc, there’s a themepack of official Win 7-tan creatively named “Madobe Nanami” and voiced by Mizuki Nana. I don’t know the first level link, so here I give the link I found which contains the themepack. In case you’re still using ancient or not-quite-usable version of Windows, you can still extract the data contained in the themepack and use them manually.

じゃじゃ～ん！

[ Download here ]