Ya.. don't overvolt it, otherwise it fries..
but keeping RAM linked, will keep it at a 1:1 ratio and automatically overclock the RAM with the CPU.. otherwise you can keep it Unlinked because you got those crappy 4gb G-Skills with 5-5-5-15 Cas 5 DDR2 800.. (it might do ok?)
but for video cards, overclock using ATiTool or Rivatuner (programs you DL)