My laptop won't start?

Hi there,

I have an Advent 5712 Laptop which won't start for me at the moment and i was wondering if you could help!
When I power it on, I get a message which says "Windows failed to start" and it gives me two options to choose from: 1) Launch startup repair or 2) start windows normally.
When i choose startup repair it brings me to a blue screen which says "a problem has been detected and windows has been shut down to prevent damage to your computer", followed by "UNMOUNTABLE_BOOT_VOLUME". It suggests to start the computer in safe mode but this doesn't work and brings me back to the Launch startup repair option!
I have consulted my manual which asks me to press F8, then choose "repair your computer" but again this won't go any further than the launch startup repair page.
I have no idea what to do next? I would greatly appreciate any advise you can offer!