Check that all cables are not damaged, have been plugged into the correct ports, have been plugged into a power source correctly and have been switched on at the power.

If your PC will not boot/load Windows remove any external drives example: USB sticks or external hard drives, sometimes your PC may try to boot from them instead of your internal drive that has Windows installed.

Discharge the device. If you have a laptop that wont turn on, has issues booting up or you can not access the BIOS settings. Remove the battery (if possible) and any other power source connected to the device. Hold the power button down for 20 to 30 seconds to discharge the device fully. After doing this reattach the battery and power source (if needed) and try booting up the device again.

Plug the device directly into the wall socket to identify if there is an issue with a power board or socket.

Update Windows to be sure all security patches and dependencies are installed.

Restart the device, sometimes updates can cause your device to lose some functionality, example: the internet may cut out and not be able to reconnect, or applications don't open correctly or at all. Restart the device so Windows has a chance to configure the changes.

Restart your router and modem, or try connecting to your Wi-Fi with a different device. By doing this you can check to see if you have a network problem or a device problem. Sometimes your network will be working correctly its just the device that your trying to connect with that has the issue. Try restarting the device and connecting again.

Accept cookies for sites clear your browser history.

Restart the application/Reinstall the application. It can be frustrating but sometimes the only way to fix applications faults is to reinstall the application again. Just make sure to read the uninstallation wizard carefully so you do not end up deleting associated files that you have personally created.

Run in the application in compatibility mode, right click the application and select Troubleshoot compatibility from the context menu and just follow the troubleshooting wizard.

(Ctrl+Shift+Esc) to start task manager and end tasks if an application becomes unresponsive, or restart Windows Explorer if the computer seems to becomes unresponsive.

Run the application as administrator, right click  the application and browse to Run as administrator from the context menu.

Run antivirus update and scan, be sure to update your security programs before you scan, this will insure that they are looking for the most recent viruses that your provider has found. Note: You can have more then 1 antivirus provider installed on your computer, but do not run a scan with both antivirus programs at the same time, as they may take up computer resource's and slow your PC, and or may crash your PC if they applications try to scan the same file at the same time. 

Run your PC tune-up or optimization task.

Disconnect and reconnect the external device/hard drive device or try the device in a different computer.

Perform a disk defragmentation to speed up your Hard drive devices (HDD's). Defragmenting your hard drives every 6 to 12 months will increase efficiency and speed.

If an application just refuses to open, right click the application, select properties from the context menu, select the general tab and check to see if the unblock check box is ticked if not, check/tick the unblock check box, then click Apply and ok.

Check Device manager to see if your drivers are installed and up to date. Sometimes device drivers can become disabled or may even be uninstalled without notifying you. If you find that your WiFi or Bluetooth function has magically disappeared or stopped working, navigate to device manager ( for windows 7 Click start > Control panel > Device manager) (For Windows 10 just type "device manager" into Cortana's search box and press enter). To check to see if your drivers have been disabled, look for the Bluetooth or Network adapters category, and click the drop down menu's arrow to see the installed devices under that category. If you see a white circle with a black arrow on one of the devices, Right click the driver with the icon and click enable. The menu will refresh and the driver should become responsive again. If you see a yellow icon with a ! sign, then the driver hasn't been installed or has been removed. If you are running Windows 7 to 10, connect an Ethernet cable directly to your PC to get internet via cable connection, then restart your machine. Once your PC turns back on, and while your PC is loading your desktop, Windows will check to see if any drivers are missing and will automatically install the drivers you need. If you do not have a Ethernet connection on your computer you will need to download the correct driver from the internet. NOTE: drivers are FREE, dont be ticked or scammed into paying for drivers. Just google your computers motherboard or model number and add the word drivers at the end of your search. Example: HP spectre x360 drivers or Gigabyte Z270X-Gaming 5 Motherboard drivers, and select the official manufactures website to download the drivers from. The drivers are usually located under support or downloads.

Running low on disk space?. Delete old files with disk clean up. Type disk cleanup into your Windows search box and press enter, then select the drive you wish to clean.

Try a different internet  browser. If your finding a web page will just not load in Firefox try using chrome or vice versa.