Another way to assign cpu affinity to each instance of Warcraft is to edit your config.wtf. This solution only works if you run each instance of Warcraft from a separate directory as you only have one config.wtf in the WoW directory (meaning that if you run multiple copies of WoW from the same directory, they will all have the same cpu affinity using the config.wtf variable).

http://forums.worldofwarcraft.com/th...78017311&sid=1