Lion Recovery Utility and Mac's HD

Hi everyone, I should ask you some advices for my iMac (2009) with Mac OS X Lion. My HD was full and I decided to reinstall the entire operative system to clean a little bit all the machine. Here the problems starts.

Lion recovery utility starts downloading a new copy of Lion but, after 5 or 6 hours, the computer restart itself but without installing nothing. I mde this process twice but nothing to do. I tried installing Mac OS X Snow Leopard, to upgrade lately to Lion, but during the installation "Controller" gives me an error. I should always restart my machine and nothign is done.

Maybe the HD could be broken, but I tested it and Lion says me "The Machintosh HD is ok".

Have you some advices to me??

Thanks

Best Regards

Dr. Enrico Catanzani