Failure to boot

I am running Karmic Koala - recently installed as my sole operating system.

After a recent restart, the login screen indicates it is doing a file check.

When the file check gets to 70%, it fails and drops to a command screen (of which I am completely unfamiliar with as I am a newbie still trying to learn).

The command screen indicates that there is a problem reading the file system.

I have no idea how to fix this and get things running correctly.

I would like to get it up and running again as I have all my programs set up nicely - and I really don't want to start again from scratch.

Any assistance would be appreciated.

Thanks,

Dickson