Hi, sorry to hear you are having problems.
1. Start up your desktop as normal but as soon as it starts keep pressing the 'F8' key.
2. You will have a black background with white writing on and lots of options.
3. Use the up and down arrow keys and select last known good configuration, then press the enter key to select it.
Your computer should start up.
If you have a blank screen, do you hear the fans whirring and see lights on the front?
If so then your computer works but is not sending s signal out to the monitor.
Check all cables to make sure they are securely connected.
If you still have no image. Swap your monitor for a friends one that you know works.
This will test if it is your monitor that has failed. If you see an image on your friends you will need a new monitor or new monitor cable.
If you do not see an image on your friends monitor and your PC has lights and fan whirring then you need to get a new graphics card.
If you have no lights and no fan whirring it is outside the scope of this and we need some more information as it could be
1. Failed power supply
2. Failed memory
3. Blown motherboard
4. Failed processor
Please report back with answers to
1. Do you hear fans whirring?
2. Do you see a power light/led light up? (in example pic it is green)
3. Do you see the HDD (Hard Disk Drive) LED/light flash at all?
Many thanks for your information