What you see here is an older default Ubuntu theme (known as "Ambiance"). This was for a release about a year and a half ago.
You can install this on Ubuntu 11.10; however, because of some underlying groundwork, You can't use the whole thing. For instance, here's a picture of my desktop using the theme:
You may notice that, when maximized, the buttons revert back to their old style. This is because this old theme hasn't been ported to the newer groundwork that was laid by Ubuntu: Since the current theme is the one used, it's the one updated :).
1) Download the "lucid-updates" deb-package from here:
You'll have to click lucid-updates, then "all" under "architecture", then a mirror to download the package from.
2) Right-click on the deb-package, choose "Extract Here".
3) In the extracted folder, browse to "usr/share/themes"
4) Rename that folder into something unique, like "Old Ambiance"
5) Here's the tricky part. You're going to need to move this into a system folder. Press +F2 to activate a command launcher. type in "gksu nautilus", then press enter. It will ask for your password and then pop another window up.
6) From the sidebar, press "File System", then navigate to usr/share/themes. You should see a handful of folders, such as Ambiance and Radiance.
7) Using that same window (you have to use the one you elevated permissions to), open a new tab by pressing +t, click on "File System" again, then navigate to home/[YourUserName] and wherever your newly extracted/renamed folder (i.e. "Old Ambiance") is. Drag and drop that folder into the other tab so it'll plop right into the folder
8) Install Ubuntu Tweak from the software center
9) Launch the program (the program's name is shown as "Advanced Settings") and navigate to "Themes"
10) The only one you'll be able to change is "Window Theme". Change that to "Ambiance Old"
And that's it! You're done.
Give me a comment if you have questions/something doesn't work. Good luck.
Revised to make a little easier (IMO).