Hi I have an Intel Imac 2007 model & Buffalo usb 500gb external hard drive. I cloned my hard drive using Carbon Copy Cloner and all worked fine until I tried to restore my iMac: I booted from the external disc, since I made sure the back up was bootable. On boot up, a Mac OS window opened up titled 'Michael's computer' and requested a user name and password. It rejected my admin user name and password. I did not set up any password for the external drive and have booted up before and have never seen this pop up window. I tried to reset the password using my Mac OS system disk as a start up disk and holding down the option key. When I got the option to reset the password, I could see the internal drive & the external drive and could reset the password on the internal drive, but the option for the external drive was greyed out. As a result I cannot boot up my system from the external drive and can therefore not restore my iMac. How can I boot into my system from the external drive? Any help would be greatly appreciated!