Imac OS X Lion - Restore
I'm having problems logging into my iMac OS X Lion 10.7.
Tried Disk Utilities >First Aid >Repair disk
Error message: Disk Utility can't repair disk....format disk and restore backup files.
Tried 'Reinstall Mac OS X'
Select disk showed 'Recovery HD' but with message 'This disk is locked'.
I am a newcomer to Apple and haven't used Time Machine.
How do I repair and restore my OS?
Am getting desperate!!
iMac (21.5-inch Mid 2011), Mac OS X (10.7)