Replying to Computers Suck; a plea for Help.

So... what does it mean when my computer says "Error loading Opperating system" and nothing else? and how does one fix it?

I really dont want to have to pay to get this repaired because frankly, I cant really afford it... although thats probaly what im going to have to do. Any help would be very much appreciated.

And no, im not on my computer, im on my roomates.