Can't install El Capitan
I've down loaded El Capitan but when I try to install it says my McIntosh HD is being used for Time Machine. I get the message "OS X cannot be installed on Macintosh HD". Is that where I'm suppose to download it to? I am currently running OS X Mountain Lion (10.8.5) I never installed Yosemite, could this be the problem
iMac, OS X Mountain Lion (10.8.5), null