The last few days my 2009 iMac is booting very very slow. 3 days ago it needed 8 minutes to boot, yesterday it failed to boot. I have already tried the following : - safe boot (holding shift during boot), - resetting PRAM, - booting from the recovery partition. I was able to boot from the recovery partition, but then it asks on what disk I want to install OS X. It shows my Macintosh HD, Bootcamp & Recovery partitions. All three are 'locked', meaning I can't choose any of them to reinstall 10.9. Any help would be appreciated ! As said before, it's a 2009 iMac with intel processor, 4Gb RAM, GeForce video card and 1Tb HD.