In addition to setting the max memory as Gail suggests, I'd want to see what your wait statistics are before and after you add this memory. Further, you want to look at the execution plans of the queries before and after you add the memory. Also, get the wait statistics of the queries so that you know specifically what is causing them to run slow. While adding memory is no guarantee of speeding things up, I haven't seen a system get slower because of adding memory.