altho you say you installed Ubuntu.....are you aware there a differents variants of this distro? (distribution)
2) Can you name the exact release you installed?
3) What other distros did you try if any?
4) Are you aware that netbooks or not-full portables do not handle full distros very well?
5) This means that to get the best out of a netbook you need to install a distro that is designed for netbooks....and designed for that particular netbook's processor
atom N270 or n280
6) No matter what....you can not afford to install full distros or distros that use a bloatware desktop environment or bloat windowmanager....examples being KDE or Gnome and Ubuntu uses Gnome.
7) Leaping ahead you may like to look at these distros and see if they are better?