Q: Grey screen, spinning wheel, the bar for a bit and shutdown!

HI everyone ,

New to posting on here so apols in advance if it's log-winded :-)

I have a 2011 Mackbook pro which is now on Mavericks. I also use Parallels. No problem till yesterday when it flashed up a screen I didn

t have time to read fully but it said something like ' problem encountered and having to shut down.'

I then tried rebooting and the following sequence occurred :

1. Switched on

2. Sound/ grey screen/ Apple logo/ turning wheel/ bar only moves about a cm across and then laptop switches off.

I then did the following:

1. Switched on.

2. CMD + R

3. Grey screen, language option, OS X utilities box .

4. Select disk, volume, image appeared

5. Mac HD (first aid) - verify disk (verifies volume Mac HD sequence)

6 (in red) InvalI'd Node Structure. The volume Mac HD could not be verified completely.

7. (Box pops up) disk utility stopped verifying Mac HD. Click repair disk.

8. Repair disk- (in black) volume repair complete. Updating boot support partitions for volume as required.

9. (In red) Disk utility can't repair this disk. Backup as many files as possible. Reformat disk. Restore your backed up files.

I tried going into Safe mode but for some reason I can't . I also tried to get into PRAM mode but also cant . Only get into Disk utility.

Here are the questions:

1. Can I do a back up by connecting my Mac to Time Machine via a Usb Or FireWire ? How do I do this?

2. If I try to reinstall OS X I get a 'this disk is locked' for both the Mac HD and Recovery HD.

3. What is the recommended next step ?

Any assistance is much appreciated !