so i have:
2ghz Celeron (478)
3x 512mb 266mhz RAM
Ati Radeon HD 2400 PRO AGP
i use 11.10 (instalated from windows) but is very slow (i use it for internet, chat, youtube and one online game)
so which version is better for my PC 10.xx or 9.xx
Maybe you'll better install 11.10 Xubuntu. Or Lubuntu. 9.XX is no longer supported, and 10.04 won't run much faster. Xubuntu is pretty fast, but Lubuntu is superspeed ;) Just figure out, test, an choose :)
That computer should be more than powerful enough to run normal Ubuntu. The question is how well supported your VGA is. You may not want to use Compiz as your window manageer. Normal Ubuntu comes with the option to load a 2D desktop, which you can access by clicking on the button next to the password field before you log in. It is called Ubuntu 2D. This uses Metacity instead of Compiz, but will still give you the modern Unity desktop.
Remember that everything is available in Ubuntu. You don't have to use Lubuntu, Xubuntu, etc. For instance, if you want to have the option of switching between Unity, LXDE and Xfce, simply click to install them. You'll then be able to choose at login. LXDE will just be added without any issues. Xfce will have a conflict with the notification system, and will warn you that Ubuntu Desktop will be removed. It's fine. It's only a warning, and only the notification system will be removed. You can just reinstall Ubuntu Desktop to undo. It's only a few KB of download.
In other words; my recommendation is that you give Ubuntu a try, and if necessary, experiment with different desktops. No need to reinstall the entire system for that.