Sony Vaio won't start up

I have a Sony Vaio VGN-FW56E running Windows 7.
All was working fine until this morning when I started it up and entered my password.
The welcome screen stayed on for over 10 mins and then it started up properly, however every icon suddenly disappeared.
The screen went blank and an error message appeared saying ;Operating system not found;.

Apart from going to PC World to see what can be done can anyone make a suggestion as to what I can do? I don't have a recovery disk.

Thanks