Hello everyone, My friend has a mid 2011 iMac and since a week, it's very slow. It's a random problem and after 2-3 minutes of use every operation is very slow (always the spinning colourful wheel). I have fresh installed and updated to Mavericks 2 times but always the same thing. Also when it was initialising the disk, there was the colourful wheel and everything was unresponsive. I suspected an hardware problem but the Apple hardware test doesn't finish so I am not 100% sure. Then I downloaded a small program to check the hard drive and the result was "failing" (SMART test). The mac is out of warranty so I don't know how much it costs to change the internal hard drive (any idea here?). I tried to install Mavericks on an external disk and boot from usb and everything looks fine. The internal disk is damaged. My question is: can I buy a 3.0 external disk, install mavericks on it, select it as startup disk and always work via usb with this disk? Any problem that I am not aware that this could cause? Thanks all!