the point is that the component which is required for installing updates, servicepacks and changing features has a limitation which doesn't allow you the slipstream ServicePacks. I've used vLite to integrate the Sp1 into a RTM DVd and next Win Integrator to sliptream Sp2 into the image and this damages the Image. When you install the slipstreamed Image it will fail reboot after the OOBE phase and will fail to boot after this reboot. That's why MS disabled sliptreaming of servicepacks in NT6.x (Vista, Win7)