I use I8KFanGUI (thats how its spelled, with an uppercase "i" at the beginning). This will tell you the current temperature of all of your components. You can also tell the computer to force your fans at high speed, or set them higher depending on if the temperature gets too high.
It will also tell you the current fan speed, CPU temp/speed, GPU temp, chipset temp, HD 1 temp, HD 2 temp and Memory temp.
I currently have a Dell Inspiron XPS Gen 2 laptop with Pentium M 2.13 Ghz CPU, 6800 Ultra GPU, and my temps are:
(all temps in Celsius, temps may vary)
CPU: 40's to 50's = average, over 70, fan goes into high gear
GPU: 55 idle, 70's to 80's on workload with games
memory: 55 constant
chipset: 53 constant
hard drive: 41 constant
I have two fans that cool the CPU and GPU.
Desktop temps may vary significantly, but these temps are my laptop temps and they are great!
Id suggest you start your computer, run the program, force the fans to high speed immediately, and check to see if the temps are out of range from research on your specific computer. If the temps are normal and it shuts down, you probably have a Virus or a hardware problem. Only way to quickly check is to insert another laptop HD into your system with another configuration and see if it still does the same. OR, you could reformat and check to see if the problem presists. Reformat as in disk wipe, not repair!... A program called DBAN will wipe your HD with random 1's and 0's therefore eliminating all your files and potential viruses! Backup first!
If it still persists, you can then check to see if your CPU and GPU is the culprit. (if you have a dedicated graphics card, this applies, but if its integrated, dont worry about the GPU).
You may need to reapply thermal compound in between the heatsink and the CPU (and possibly GPU) if their temps get way to high as shown in I8kFanGUI. If they are the known culprits, you can try "arctic silver" thermal compound and reapply it. If you are not comfortable with opening your computer, find someone that knows how to do this.
(If its under warranty, dont worry about it and let them fix it themselves!)
Hope that helps!