fresh installing of 10.6 did not finish and cannot start my imac

Hi there,

i had problems recently with my Imac (running osx 10.6) so I bought a brand new disc osx 10.6.3 and decided to format the Imac and run a fresh reinstall from the new disc (i could not find the original).

Everything went ok (successufully erased and installed) until the Welcome pane for the setting up appeared, where I was asked to select the country. Once I did that, the screen got completely stuck so after waiting for at least 30 mins I shut down the Imac forcing the shut down key .

Now it is worst then before!!

Sometimes it starts with the usual question mark folder, sometimes with a grey screen.

I have put the installation disc again in and trying to reinstall the osx BUT it simply does not respond to any keys! (I tried holding C, then option key....)

Please help!!!!!!

What shall I do?