It's got nothing to do with Wwindows itself, and everything to do with DirectX. Without dedicated graphics hardware (Hardware T&L, particularly), anything needing T&L (most Direct3D games) is going to be much slower than it would with a 'real' graphic card or chipset. As such, Intel integrated graphics are pretty poor even under 'real' Windows. And running with a virtualization layer may not make a huge impact, but it certainly won't help performance.