I have two WinXP VMs running both in coherence mode, I use them to play online games. In Coherence mode with an XP taskbar visible on the right and left sides of my monitor, I see considerable lag when I have games from both VMs on the screen. In fact it's so unbearable it's made playing them virtually impossible. When I have both VMs running but only one with an active window on the screen I see virtually no lag at all, so I'm pretty convinced something between the two VMs is clashing causing the lag when an active window from each is present. I have a 2006 gen Mac Pro, with 16GB RAM and an ATI Radeon HD 4870 512MB video card. I've allocated 3GB to each VM, 128mb video, enabled 3d acceleration, hypervisor enabled, tune windows for speed, optimize performance for virtual machine, and power consumption at better performance. The VMs are very clean and recent installs with no antivirus or anything else installed other than the gaming software. Someone please help!!