The problem isn't as much Linux fragmentation as that the task of which he wants to accomplish is something almost any Linux distribution does the same as the next. Anything that doesn't come with a full-on bloat DE like KDE4 (KDE4 base install would probably be fine, but with all the bells and whistles it'd probably bog down that netbook bad) Same with Gnome3, and the like. Though, Compiz fusion would probably not perform poorly on the machine, it'd cut battery life a tiny amount. I'd personally go with something with a lightweight tiling window manager, and use multiple workspaces like mad. The limited screen real estate warrants excessive use of workspaces. If I were to pick a pre-rolled distro, I'd go with ArchBang, if I was doing this myself though, I'd start with an Arch base install and build it up how I like it (which I have started writing scripts to do some of the more generic stuff for me...) At any rate, its not really a question with an answer, basically lightweight + personal preference = what you want. And pretty much all distros can be configured to do what you want them to. If you are more accustomed to Windows, and enjoy using a pointer - go with a LXDE based distro, if you are familiar with tiling WMs and like a lot of configurability and keybinds - use a *box or DWM/Awesome/etc... based distro.
