Q: g5 freeze

Hello !!

I have a G5 dual core 2.3 with 2Gb Ram.

I tried to install tiger osx and leopard they both keep stuck after 2-5 mins of use or immediately when trying to web browsing .. the mouse icon turn to rainbow sppining and i can move the mouse but can't do anything else everything freeze , I also tried to move the ram sticks to other slots & tried to put another 2 old ram sticks and replace the hard drive but with no succses ;/

Any ideas ?