1. Honestly, by this point you do not need a Virus protection as you can not enter the windows operating system. I have repaired many computers with this situation and trust me, it is quite simple.
2.

When you turn on your computer, make sure that the fan in running in the very beginning. If it is a virus that attacked your computer, your fan will continue running without anything on the screen. Your fan is located in the back of the computer. That is where the power supply is at.

3. If your fan is still running, you must reinstall your windows operating system. Please note, do not do this until you read my next article, 'How to save your files from an unworking PC'.
4.

If your fan is not running, then this is good news for now. You must turn off all the power from your computer. I recommend you unplug the power cord behind the PC. You are going to have to open your PC
5.

The other reason your computer might be turning off is because the computer is over heating. The CPU is not getting a lot of air flow, when you turn on the computer, and when it goes into the operating system, the PC temperature goes up high, that's why computers need fans. But what is causing the PC to over heat? Well, its DUST!!!
6.

Its time for a PC clean up. Get your paper towel and q-tips. Have your magnetic strip handy, or if you don't have a magnetic strip, touch the power supply to ground your self from any electro magnetic shock.
7.

Get your q-tips and clean the Dust off your CPU fan. The air is not going through to the CPU, that's why the computer shuts it self down, so that the computer would not catch on fire. Clean every hole on the computer case, make sure its clear for air to enter. Your CPU fan should look like the picture.
8. Clean all dust off of the computer case. Once you are done, close the computer and plug everything back in. Start your PC is it should load up.
9.

If non of this worked, you must open the computer case again and make sure all the Divers are plug in securely. Many times a technician installs a new drive or RAM into your system and it wasn't properly installed. Your computer will not start. Make sure the RAMs are nicely secured in the PCI slot. Make sure the 2 white side handles are inserted correctly on the ram as shown on the picture. Close your case and start your computer. That should work.
10.

If that did not work, it may be your RAM or Motherboard. You must go buy a new motherboard or Ram. I suggest you take it to a technician to install the motherboard, but if you know how to install a new one, good for your. Remember to back up your data. Very Important.