Well, you can start here -
Open a Console/Terminal (Crtl | Alt | T) and type
sudo apt-get autoclean
sudo apt-get clean
That'll clean your package cache and probably reclaim a
couple hundred megabytes. Won't take more than a couple of seconds.
I think the ASUS cleaner you mean is a program that cleans and reorganizes things (rather like similar programs in both Win and MacOS) and, like them, the default seems to be set at a bizarre time that, almost invariably, computers are not running at. In the Eee's case, it would seem they've even disabled that run and hidden it's GUI (what button do you have?) so you can't set the schedule.
In my experience, running the below (at the obvious schedule) seems to help and I believe this is the program you mean -
In Terminal -sudo run-parts -v /etc/cron.daily
This takes the longest. Don't panic. You'll see the SSD light flickering if in doubt and you will eventually be brought back to the prompt.
sudo run-parts -v /etc/cron.weekly
sudo run-parts -v /etc/cron.monthlyHope this is what you mean and that this helps!