Computer blacks out

i just got my old laptop back from fixing and i reinstalled windows vista basic after i downloaded wow started the game and i played for about 3-5 mins then suddenly my computer screen turns black and i can hear wow sound for the 3secs then it turns like to sleep or somthing and i need to turn off and on again the computer to use it again it happens with every game even the old ones like spore age of empires stuff like that my dad told me that i need a new graphic card and more ram i got 1790 ram and prossecor: Intel (R Pentium(R Dual CPU T2390 @ 1.86GHz 1.87 GHz. if that means anything. A friend told me that its my vista and i dont have enough ram for my vista or that its an old version of vista and suggests me to use xp, so my question is what to do to buy a new graphics card and more ram or to change to xp ah and btw i checked on and it says i can run wow cataclysm but not recommended, so please help it drives me nuts.
thx :

Your gpu is overheating or is going bad. Or something else is overheating.
Maybe do some cleaning?

FAIL (the browser should render some flash content, not this).

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