Will not boot from HD

Hi reutthe,

Unfortunately it sounds like your HDD is either dead, or for whatever reason has become unplugged. If it is still plugged in, it most likely has died. Moving parts HDD's will eventually die over time and need to be replaced.

Just for kicks, I am going to bet that your iMac has been running slower and slower over the last 3-6 months. If this is true then your HDD is dead. If not, it still may be dead, >.<.

Let's get to the upsides;

Carbon Copy Cloner will make your transition to a new HDD painless. (it should) Buying a new HDD (moving parts) is a bad investment in my opinion. As you should be looking to buy a new drive, I would recommend moving to a Solid State Drive (SSD). This will eliminate a moving part inside your iMac, but also it will increase its loading speed tremendously. If you are a person that keeps lots of media on their computer, you have options there as well. SSD's come with smaller amounts of storage at a higher price, so generally you want to stick with a 120 or 250gig drive, and migrate all of your media (pictures / music / videos) to an external HDD to save space on your SSD.

Good luck!