Compiz comes with Unity or Gnome?
 

Hi, I want to get Compiz running on one or two computers. One has 6 gb RAM na the other 500 MB RAM.

Do I download Unity or Gnome Ununtu or another distro, with a view to using the net, documents and maybe studio works?

As compiz is a separate entity you could ultimately download whichever distro you like and I believe it can connect to a number of environments

which ditros have it pre-configured?

Haven't played with main stream distros for a while so you would need to look that up.

Ubuntu has compiz by default with their stock Unity graphical interface. The current compiz is not compatible with the new Gnome. So in a distro like Arch you can install Xfce and install Compiz and set up Compiz as Windows manager for Xfce.

I dont know if other distros keep Compiz in their repos other than Ubuntu.
I guess you could go with Xubuntu or Lubuntu and install Compiz from the repo. KDE has lots of eye candies on their graphical interface too. Very similar to Compiz.