First I'd search the net for a offical wallpaper or such that has the logo on it, since I'm sure you've already done this I'm guessing exracting it from a emu is your last option. You'll want to enhance/alter the logo because it WILL look VERY blocky. Best bet is to try the filters that come with the emu first. I have good luck with the "Super Sai x 2" filter. If you still aren't happy then it gets really tough. You'll either have to
a. Pull off some photoshop magic
b. redraw the whole logo
c. get back onto google and try to find the logo again