Just want to point out that 32 bit XP and Vista are limited to 3.5GB of ram or so due to physical address range limitations. If you want more ram, you need to use 64 bit versions. WoW can use as much as 1GB per copy. So 2 copies on 2GB machine will eat up all your ram. 3 copies will still run, but it will cause lag due to swapping of memory to hard drive. You can slightly improve it by using RAID 0 as your main drive. But only real solution is to switch to 64 bit version of OS and have a lot of physical ram installed. Like 1 gig per copy of WoW. CPU is not very important as long as you have only one copy of WoW running in foreground.