You're going through wow64, the thunking layer. Microsoft, in their infinite wisdom, didn't implement their stuff in the same manners that we did. When you execute a 32-bit application, all calls are not to native 32-bit libraries, but are actually thunked to the 64-bit space. Now, while it's not the same performance hit that the 16-to-32-bit thunks were, there's a hit and you're not running in 32-bits for everything like under Linux. Now, the drawback: You have to have the multilib stuff in place on Linux or you can't run 32-bit apps. Under Windows, you can run always. But there is a performance, etc. hit and a risk of it just not working right.
I got Ubuntu 9.10 running on it with some issues however:
The microphone didn't work, but did after I installed the latest ALSA from source.
The N330 doesn't support Speedstep, so there's no power scaling in Ubuntu. Asus does have a power scaling app for Windows 7 though.
WIFI didn't work, until I downloaded the driver from the Realtek site.
However everytime I started aMSN, the WIFI connection would break permanently. Only a reboot could re-establish it each time. Since a stable WIFI connection is crucial in my case, I had no choice but to dump Ubuntu and reinstall Windows 7 (32 bit unfortunately).