kayjayaitch

Q: Erasing hard drive and reinstalling OS

My mid 2011 iMac (OSX Yosemite 10.10.2) has been getting very sluggish despite ensuring sufficient spare space (currently 200Gb) and running the basic Disk Utility verify/repair routines. So having done a full data back-up I am now trying to erase the hard drive and reinstall the OS. Following the recommended steps in the Disk Utility I get as far as the erase disk stage but then an error message pops up saying "couldn't unmount disk". Has anyone encountered this before or have any suggestions please?

Posted on Mar 11, 2015 5:58 AM

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