Game locks up

[searry]

The demo ran fine I have bought the game, I get to play about 5 mins, then my computer starts bleeping like a jerry springer show and my mointor shuts off. I read this in the read me.

'4.1 Game crashes into Blue Screen

The game may show instability on systems with 1Gb RAM, Windows XP, and anti-virus software installed.
Please expand your RAM, uninstall anti-virus software or install Windows Vista to solve the problem.'

Now I don't get a blue screen, I may do but as the monitor shuts down I couldn't tell you. I have 4Gb RAM, so it can't be that, I have un-installed my anti-virus software and it's not that. I have XP installed and as it says under the System Requirements (Recommended) OS: Windows XP/sp1 (Windows Vista), from this I am running the recommended OS. If I am now told that my OS is the wrong one, then I would like a free copy of Vista please, as I bought the game in good faith by what I read on the case.