it will run just fine, except the current PC3200 stick you have in there at the moment, will be reduced down to PC2700 (DDR333 instead of DDR 400) speeds as the RAM can not run independent of each other, and by default the memory speed is reduced to the lowest SPD rating, which will be your PC2700 RAM, there will be a performance hit, but having more memory will benefit you more, as this will mean less use of the swap file ..
