- Monitor suddenly does not have any display.
- CPU starts then shuts down or restarts after being used for a short while.
- CPU starts but does not show to boot and monitor does not have any display.
- CPU shows error or BSOD shows or freezes on boot up.
If it is not the RAM cards, re-seat the GPU or video graphics card. If it still does not work, test the graphics card on a different CPU compatible with it. You should be able to tell then if it is the graphics card that is at fault or not.
Lastly, check the heat sink and fan of the processor. Chances are dirt and dust have accumulated causing the processor to overheat. Follow instructions from the manual on how to properly remove the fan and/or heat sink. To clean the assembly, use a soft bristle paint brush to get rid of the dirt. If the processor is exposed as with AMD processors, you should be able to see if silicon paste needs to be added for better cooling.
Take time also to inspect the PSU for dirt accumulation. It will also need to be cleaned gently with a paint brush. Take extra precaution in cleaning as some parts of the PSU still hold some high voltage that could give an unpleasant shock or even a bad burn.
I am currently handling and maintaining 12 desktops and 2 laptops at our internet shop and the above were the frequent problems and solutions.