My computer keeps on hanging or abruptly shuts down.All the fans are working out correectly and no virus infection.

It is either running hot or you have a virus or infection.

Sounds like it might be running hot. If it is running hot it shuts off to keep from damaging the motherboard.

If it is running hot it will boot up to windows and let you do things as long as it is cool, but when it gets hot it will shut off and not boot up again until it cools off. That's a sign that it is running hot.

Three things that will cause it to run hot.
1) Dust. Dust in the vents, inside the computer, clogging the fans and dust around the cpu and heatsink.
2) A fan that has stopped working.
3) The Thermal Paste around the CPU and Heatsink has dried up or is too thin to keep the unit cool.

To fix either of the three would require taking the laptop apart. However you could buy a can of compressed air and blow out the vents, but this just pushes the dust inside the computer, but it might work.

If it is not running hot then you have a virus or infection that is shutting it down. Download and install MalwareBytes and run a Quick Scan.
Go to www.google.com and in the search box type:"Download cnet Malwarebytes" (without the quotes). Download andinstall malwarebytes from the sites download.cnet/malwarebytes. When the site opens up click on the Green Download button on the left. Do not click the Red Download button, that's junk. When it finishes installing the Gui Interface will open up with an offer to Accept a Trial Version or Decline. CLICK DECLINE you want the totally free version. Run a QUICK SCAN. As it scans, if it finds infections the number will be in red. When it finishes scanning, click SHOW RESULTS. A notepad text document will open up showing you the results. You can close the text document and go back to the Gui Interface where you will click REMOVE SELECTED RESULTS. The objects will already be selected for you. When it finishes removing the objects click ok and it will sometimes reboot your machine.

it is either infected with a virus or it has some hardware issues. try reseating the ram. another common issue is if the fan is dirty which leads to overheating resulting in the laptop shutting down frequently. try to clean it with a painting brush & vacuum cleaner.

increase ur ram Scanning computer to eliminate malwares, spywares and the viruses from your laptop.
2- Repairing and cleaning Windows registry.
These two tips are found to be very helpful to fix the laptop shutdown problem. Almost all the computer users surf internet which could result in viruses attacking your system. Some of these infections are really pesky and cause the machines to shutdown randomly.
The registry errors, however, are the internal errors and can become a cause of system crashes and freezes. The registry keys shall be in good health to keep a system perfect.
When I noticed my laptop keeps shutting down everytime, I tested the Intel Software Partner, RegInOut to fix the random shutdown problem with my laptop.

First It may be a hardware problem, mostly when computer fans is not runing the computer will shutdown, to protect it from damage.

Second It may be a cause of virus infection that leads the computer to shutdown and reastart again.

so you must check if your fan is working correctly, also scan your computer from virus

Abrupt shutdown commonly is caused by overheating. This is mostly caused by a faulty CPU fan. Check if the surface of your laptop gets warmer than usual. If so and if you are accustomed to disassembling electronic devices disassemble the laptop and clean the fan and heat sink. Otherwise visit a technician.

Does this occur when you open a specific program for eg. windows media player etc. Note that the application may open and run for a while or even run perfectly sometimes, but observe if the abrupt shut down has any relation to a specific program. If so checking you Ram or using an alternative software will resolve your issue.

NOTE: Some viruses may cause such actions. Scanning your computer with the latest virus definition updated anti virus may solve your problem.

Possible causes of the problem:
- System overheating
- Virus infection
- Power supply malfunctioning

Solutions:

- Check your computer if the fan is properly working.
- Scan your computer for viruses
- Check your computer power supply by a qualified technician
- Reinstall your computer operating system

Try this also:
From the run box you can type shutdown -a and that should stop it from shutting down long enough for you to fix the problem.You need to look up how to remove msblast from your computer.

You haven't mentioned if it turns off abruptly or shuts down telling you that the PC is shutting down.

- When your PC turns off abruptly, its mostly the CPU which heats up. The reason may vary from the CPU fan stopped working to CPU gone bad.

- If its a proper shutdown, most probably there is a virus on the PC.

KIndly feel free to ask me if you need further clarification

regards

Sandeep

If you have recently fitted new hardware. Take it out.
If not, buy a power surge protector from your local pc store

It sounds that you might having problem with your power supply unit, try replacing it with another working one. Problems like this one can be caused by defective power supply unit.

scan your system with antivirus maybe your computer is infected with virus.

If this not work, try examine the memory, remove clean and fix it back and start the computer.
if still thesame;
examine trhe mainboard maybe some part of it overheating.
if non of those, then remove newly install hardware and software
id still theamse happen, i recommend you to reinstall your windows to correct all the errors.
It pretty if you reformat it before installing the new windows.

Note: reformatting and reinstalling could remove the important files, make backup before proceeding.