Sorry to inform you of this, but the L866r supports a PIII Coppermine up to 997MHz and PC133 SDRAM up to 512MB. You will not be able to do what you stated with the motherboard that came in this machine.
A P4 machine is what I first thought you meant -- "upgrading to a 3.2 ghz processor with 4 gb ram". After upgrading to the one GHz and 512MB, antiX-M8.5-i686 is one of the better choices for a GNU/Linux OS. Go HERE and bookmark the page -- it is one of the better ones for Linux downloads of all sorts!
Best wishes and get a later P4 or better to game on! The L866r is good enough for surfing the net (install bastille first thing to get some protection against hackers, though) but not for modern gaming. A good one to learn on!