Here are 3 things you can check right away:
1. Check to make sure nothing is blocking air vents if possible (for instance, place the laptop on a smooth, hard surface for running it, and make sure nothing is at the sides. If that works, it was blocked air flow.
2. Check to see if you hear the fan running at all - especially when the machine gets hot (some laptops do get very hot - it seems they are getting much better at not getting so hot, lately).
3. Another thing to check is the AC power adapter and/or battery - it is possible it's an electrical problem.
Another note: try posting your Laptop model# here, so others can possibly better trouble-shoot it based on common occurrences with that particular model.
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"If to err is human, then I must be some kind of human!" -Me