I have the option to start with windows xp professional setup when I first boot the pc. In fact, it selects it as default and if you dont change it to the normal OS in about 5 secs, it will start the setup. My boot.ini file reads as follows:
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /noexecute=optin
C:\$WIN_NT$.~BT\BOOTSECT.DAT="Microsoft Windows XP Professional Setup"