That's very good to know - thanks.
So, if I'm running XP Pro / Q6600 / Gigabyte DS3P / GeForce Ultra5700, it's more cost-effective now to buy 2 of the 2gb kits rather than 2 x 1gb plus 2 x 512MB (2 x $41). Not to get too off topic, but will XP be able to benefit at all from the 4th gb...