Like this Nanami Madobe wallpaper? You can get the original (1680 x 1050) here.
If you don't already know by now, Windows 7 (Windows 6.1 actually), Microsoft's latest desktop operating system (OS), was given an official mascot for the Japanese edition, to cater to the geek culture of OS-Tan, which is basically a personification of an OS. Pre-Win7 OS-Tans were unofficially created by fans, but for Win7, MS wanted to be part of the culture and hence created Nanami Madobe. We first blogged about her here.
Prefer this wallpaper of her instead? The original (1920 x 1200) is here.
Now she has her own anime, albeit a short one to promote using Win7 as a SFF (Small Form Factor) or HTPC (Home Theatre Personal Computer). Take a look @ her in action in this YouTube video: