Wow Circuit City needs to upgrade their pics, lol. The picture on the CC page you linked is standard SD RAM, but in all the options its DDR (SD-RAM). Just so long as its the same stuff (Kingston Value DDR400), and that its still just a single 1GB stick....then yes it'll be just fine to add it with your current 1GB Kingston ValueRAM stick
. But ONLY run those TWO sticks, and just those two.
And yes it does matter. In my experience its best to use the black slots on the board (the two matching slots furthest from the CPU socket). Just make sure that they are in the same color, and it'll run properly.
After that, we can all give you a hand at overclocking that puppy!
And if you haven't already, might want to check out my sig and join up at the 939 club here at OCN
. There's ALOT of members (that's an understatement) that still rock 939 setups here, and 99% of them are all in that club
. You've got the potential to have a great 939 rig....you just need some matching RAM (2GB is fine), and you're set to go!