I just purchased an AMD Athlon 3000, 512 Mb RAM, 80 Gb hardrive, and it has the DX9.0c system. It's all just a standard XP package. Obviously, I know almost nothing about internals, but have a buddy who builds his own. What specifically do I need to upgrade my computer to allow me to play Half Life 2? I purchased it directly, online, from Valve and have the full Steam setup.