I have no idé whats wrong, I want to install Snow Leopard(from the external) on my Core2duo Macbook pro, which is running Leopard at the moment. I have a Snow Leopard image, and I have used Disc utillity to partition the external harddrive (GUID), and I assume the partition and install went well on the external, because in Disc start the external appears as OSX 10.6. Then the problem: The macbook wont boot from the newly made external it just gives me this sign (of couse without the colours). I have tried to start the macbook normal, and with the option key held down were the external pops up. I have also tried to chose the external in disc start and reboot with no luck. I have tried to start the Snow Leopard install(external) within Leopard where the install start fine, but when it reboots and wants to continue the install, the sign appears. The external harddrive is a 5400rpm 40gb 2,5" which is only powered by the usb port maybe thats the problem?