Back when the Eee community was just starting up, when we wanted to install Windows XP on our Eees we had to rely on the Eee User Wiki to make sure our Windows installation runs as smoothly as possible. Every tweak we ran on the Eee we had to do manually, and it sometimes took a full day to finish optimizing XP for the Eee. It was fun, of course, but when we had to do the same tweaks repeatedly on different netbooks, it started to become tedious.
Asus apparently thought of us who had to do the same tweaks over and over again, because they released a small utility called Eee PC System Shrinker that scans your system for unnecessary files that you can delete to free up space.
You can download Eee PC System Cleaner here.