When the screen said Press enter to install or f8 to boot options or something..

If i press enter white screen with an apple logo shows up, and after 2 minutes a stop sign comes up.

I rebooted, and tried pressing f8, and enterd -v in the boot line.

a whole lot of text comes up on a black screen, and after 1-2 minutes this comes:

Still waiting for root device.

every 2. minute.

Waited for 2 hours and nothing happens.