SLI Switching Under Windows
The Asus Ai Selector tool allows you to change the graphics mode directly in Windows XP. However, all it does is make changes to the CMOS, which means that you need to restart the system anyway. After reboot, the NVIDIA drivers will detect the new SLI capabilities; enabling driver support requires a second reboot.
As you want the graphics driver to support SLI, the system needs to be restarted.
Ai Boost For Overclocking
The Premium edition comes with the Ai Boost tool, which is an on-the-fly overclocking utility.