EMS III :: Switching from the Mac to the PC

UT Electronic Music Studios - Studio III

If the computer is off, turn it on while holding down the option key. This will bring up a screen that allows you to choose the boot partition.
If Windows is running, there is an diamond icon in the system tray. If you click and it, it allows you to restart in Mac OS.
If Mac OS X is running, you can open the system preferences and change the startup disk to "Windows".