HD Install :: have i ruined it! Boot screen frozen

Yes, I have done that. And tried several different commands.

It starts booting linux, goes through normal ugly PC boot thing then it just stops and a command prompt just flashes and you can type stuff in.

I know I'm excellent at describing the situation, but i presume I'm doing something basic wrong that an experienced user would be able to spot very easily.

Is there a walk through someone can point me to?

I presumed that all you had to do was type a boot command and press enter and a live linux would boot. Why am i having problems? Is it something to do with GRUB? What is GRUB?

Thanks. I hate learning curves!

original here.