Just a note, 5-boxing with 4GB on Vista 64 I ran out of memory and started hitting the pagefile. This usually happened when I went to a few different Outlands zones. It seems a lot of data is cached and eventually you run out of memory. I upgraded to 8GB and now I have zero problems except for the very occasional loss of one follower in Shattrah. Still can't fly on epic mount with crusader turned on though.