Hello, everybody. I have an Intel iMac with with Snow Leopard and Windows 7 on separate partitions. Recently I have acquired an external USB hard drive. I formatted it with Ext4, and installed Linux Mint to it. The installation went smoothly, but I can't seem to boot from the USB drive anymore. Holding down Option on start-up only gives me two choices: Mac OS X and Windows. The drive isn't recognized in either operating systems anymore: on Snow Leopard I get "The disk you inserted was not readable by this computer" and on Windows, it doesn't even show up in My Computer. I would appreciate any help. Thanks!