Computers help: my computer turns off all by itself randomly. - Help.com

You might have a heating problem, if you can, open the case and make sure the heatsink is clamped in place properly, and that the fan are functioning

There could be a problem with the power supply, but it sounds like a heating problem to me, I used to have the same thing happen if I had more than 1 process open at a time, turned out the bracket my heatsink clamped into had broken.

anyways, you need to figure out how hot the processor is running, do this by restarting the computer, there should be a screen that pops up before windows starts booting up, telling you to press one of the function buttons (like F1 F2 etc.) to view the menu, once you’re in the menu look for something like “Hardware monitor”; If you find that, it should tell you how hot the processor is. it should be be somewhere around 40 or 50 Celsius.

if it is indeed a power problem, then you got to have it checked up at the local repair center. I doubt if you can fix this yourself. On the other hand, if it is some inconsistency in the OS thats causing this, try the following :

1. Click on the start menu
2. Click on help and support
3. A window “Help and Support Center” will open up
4. Click on Undo changes to your computer with System Restore (located in the Pick a task section)
5. click on “Restore my computer to an earlier point”
6. Choose a date (ideally this should be the date before you started having problems and see if any date is highlighted. You can only choose a date thats highlighted. Mind you, you may lose upgrades but the roll back will help if its an inconsistency with the upgrade)
7. The rest of the instructions are simple.
8. The computer will restore to an earlier date and power up.
9. That should start up your computer normally.
10. If it still has the same problem take it to the local repair shop.