Q: Trouble to boot my iMac

dear community,

since a few days i've following problem: when i try to start my imac (bought end of 2010, using the latest version of os x) the desktop only sometimes starts. if i'm lucky and it starts, it freezes immediately. the same happens when i try to start in the safe boot mode. i also tried the Apple Hardware Test, reseting NVRAM etc. the only thing which is running, is booting from cd. i can open the disk utility surface but always when i try to make an image from my mac-hd, i get error messages (like "no space" - i've plugged in a 2 tb-hd, formatted for apple with the disk utility (the internal hdd has only 1 tb); or error with in-/output).

i'm standing on the wall as you may imagine... the only thing i want to recover are all the photos from iphoto, all the rest... i would survive. ok, some other things (like musics, some documents etc.) would also be great to save but firstly i want to save my photos!!

i hope, someone has an idea and may help me out of this mess.

so long, sharo

ps: be sure, up from this restore i'll make a backup on weekly base...