I am a new iMac owner and am really enjoying Leopard on my 24" iMac. I used Bootcamp assistant to create a windows partition for xp. When I reboot holding the option key with an external usb hard drive and external usb dvd burner attached, a blank white screen is displayed. I disconnected all external non apple usb devices, installed xp and rebooted. I can boot either Leopard or XP as long as I do not reconnect the usb drives. If the hd or burner are connected, I see the Windows and OS X operating system choices but the computer freezes after clicking enter and neither system will boot. I have removed the bootcamp partition and the system will boot quickly into Leopard will all external firewire and usb devices attached. Any help will be appreciated.