Review: VMWare Workstation 5.0: One feature I hadn't noticed before: "VMware moved memory-sharing technology from their high-end GSX and ESX products into this workstation release to make teams more feasible for typical developer workstations. With memory-sharing, if you're running, say, two copies of Windows XP with each one allocated 256MB of RAM, you're not likely to take up 512MB of physical RAM. That's because VMware knows what's on every RAM page, and it will only keep one copy of any page that's identical between the two virtual machines. If the two machines diverge for some reason, the page gets cloned and each VM gets its own copy at that point, but in the meantime your physical RAM is used much more sparingly"  4:17:56 PM