The problem is always due to the graphic card failure. I have a lot of experience with this problem.
Its simple as this.
1. If you have an external graphic card and you get this problem. Then probably your graphic cards busted.
2. If you have an integrated graphic card and you get this problem. Well, Sorry but its about time you replace your motherboard
Integrated graphics are not fixable.
3. If its the external problem. Then switch
to the integrated graphic card (Thats if you have one) or get a new graphics card
either with your warranty (if its valid) or buy one.
1. (Only for external graphic card holders)
This problem is very common due to dust residing on the graphic card/graphic card slot
. Just take out the graphic card, and with a paint brush clean the metal parts and the graphic card slot. Be very careful when doing so as this slot are very delicate. Do so at your own risk.
2. This problem may occur if you computer heats up very much.
*Clean up the insides of your Pc with a paint brush at least once a month. (Due to Dust)
*Try hooking up an extra cooling fan
to your Pc to reduce the heat.
*Keep your Pc in a well ventilated area such as close to a window.
*If your Pc is a expensive one, try installing a liquid cooling system to it. May at least cost 300$.
Hope this helps.
Happy New Year!!
Greetings from Sri Lanka. :D