How old is the laptop, what model is it, what CPU has it got and what graphics does it have? These bits of information can give us a good idea of what can go wrong in a laptop to cause crashing. Depending on the age, it could be everything.
If you have a little more knowledge of computers, it would also help to upload the crash dump file generated each time the laptop crashes.
Not really old, just bought it a couple weeks ago. An HP Laptop with AMD Vision and Windows 7 64 bit on it and a AMD Cpu.
I don't have good experience with HP. The last HP laptop I had was AMD too and it overheated and turned off from just watching youtube videos in the lowest quality.
The Acer I got to replace it runs very cool, the temperature is literally 40C lower (no exaggeration)
The only thing I can suggest is to throw out the HP, I even RMA'd the HP laptop I had, they replaced the mainboard and it barely helped at all.
Of course, it's not guaranteed that your issue is related to heat. I suggest downloading CoreTemp or SpeedFan and monitoring temperatures regularly when using the computer, and you'll quickly find out if that's the issue. My old HP idled at 70C and got up to 100C+ quickly under load (it turned off at around that point). The Acer idles at less than 30C and goes up to about 70C under load. If your temperatures are around the same of my old HP you probably have the same issue.
If it's heat related, which it most likely is, there's probably not much you can do about it short of replacing the laptop with something else.