It would most likely screech to halt at startup. Steam loves resources and memory along with the latest NVidia or Catalyst onboard with the minimum of a 128mb video card. Plus it would run slow on the old Socket A model cpu you currently have. I know that from running Steam's Source with an XP3200 and 2gb of ram with an ATI 256mb video card and an Audigy 4 Pro for sound. The present cpu and video card are each the third this case has seen just from running HL2.