**slaps forehead**
Running one 1gig stick in single channel mode will give you about a 10 to 15 percent lower performance than two 512mb sticks running in dual channel.
Buy 2 x 512mb sticks
or
Buy 2 x 1024 sticks
or
Buy 4 x 512mb sticks (lowest latency solution, BTW and route I chose using Corsair TwinX XL Pro 2-2-2-5 timings)
ONLY!