I have a 512 MB system, and I would get severe slowdowns in RTW v1.3 after playing for a couple of hours. I don't get those slowdowns under RTW v1.5. With RTW v1.5, the RomeTW.exe uses about 250 MB of physical RAM and about 300 MB of virtual RAM. This leaves me with about 50 MB of physical RAM free. I have seen the RomeTW.exe grow to 300 MB when there was more physical RAM available. I haven't seen my total virtual memory use go over 600 MB while running RTW v1.5. Under RTW v1.3, my virtual memory use would be up around 750 MB when the slowdown was occuring.