Device Freezes: Phone, Computer Keeps Freezing (While watching a movie/playing a game)

If your computer started crashing after you had installed a new CPU, this could be a result of a poor application of thermal paste. .

Remove the heatsink carefully, clean the surface with a cotton ball and alcohol to remove the previously applied thermal paste, and reapply a new one.

The thermal compound fills the microscopic valleys on the surface of the CPU and heatsink in order to provide full contact between the two components (heatsink and CPU) and to decrease the CPU temperature.

This tutorial should help you if you are not sure how to apply thermal paste:
Desktop:                                                                                                       Laptop:

Note: Buy an UNPACKED thermal paste (compound) from a computer store.

If your computer has video problems (such as black screen) when it comes out of sleep or hibernate mode, the network driver's power management settings may be causing the problem. 

To change the driver's settings:

1. Open the Device Manager (right-click the My Computer icon -> Device Manager, or type Device Manager in the search box in Start menu)
   
   
2. Select Network Adapters, right-click one of the entries (eg. Realtek) and select Properties
   
   
3. Click on the Power Management tab, uncheck the Allow this device to wake the computer option and click OK

Maybe your device crashes or freezes due to lack of disk space.

Check out the Running out of disk space / no space left solutions to learn how to free up disk space.

Computers get hot. Everything inside a computer generates heat, and heat can cause component instablility (RAM, CPU and etc.) and crash your PC.

If the computer case is too hot, check if all your fans are spinning properly (you know by listening closely: do they make a sound?). Make sure that all of your computer's vents, grates and filters are unhindered by dust, pet hair, and other materials that prevent proper airflow. If you find any problematic areas, use a can of compressed air to clear the airways.

If you use a laptop, make sure to place it on a hard, flat surface that won't "smother" the chassis around its vents, thus restricting airflow.

Note: Be very careful while you are cleaning your computer because it is possible that you detach something (usually the SATA cables in desktop-computer cases are prone to detatching). Double-check everything before you turn your computer back on.