When a computer freezes, it removes your ability to control it, meaning that either the keyboard or mouse don't respond. There is also what's commonly called a blue screen of death (BSOD), which also freezes the computer before shutting it down. There are several causes for freezes, and a few ways to prevent them. However, you will always have to restart the computer when it freezes.
There are many reasons for a computer to stop working. However, it is usually because all available resources have been used up, or a program or piece of the connected hardware has caused it to freeze. Generally, it will be because of one of the following scenarios: the RAM (on-board chip memory combined with the paging memory) has been used to maximum extent or the CPU (central processing unit) is at 100 percent. In other words, the processor or memory is working so hard that nothing else can work. Other causes include a badly written driver for an accessory, outdated or inappropriate drivers.
Reasons for Maximum RAM Usage
Some programs use a lot of memory. Programs like spreadsheets and graphics programs use more memory than others. If you use these kinds of programs frequently, buy the maximum amount of RAM for your computer to help prevent freezes. If you already have the maximum memory installed, a virus or a new program may be using a lot of memory. It is possible you have a virus or malware on your computer that is causing the freezes.
Reasons for CPU to be maxed out at 100%
Other Reasons For Freezing
Your computer's memory chips may have worked loose. This is more appropriate to a desktop than a laptop, since the memory chips in a laptop are held in tightly in place with spring-loaded guides. However, check this if the laptop has suffered a severe fall. Memory chips should be cleaned and reseated, because this is a common reason for freezes on a desktop computer. Another reason for a computer freezing is that you have plugged in too many peripheral devices, such as controllers, cameras, scanners and printers. Usually, this problem will cause the computer to fail to boot (start) correctly. Try removing USB devices or a IE1394 (firewire) devices, one at a time, until it boots. A blue screen of death, which locks up a computer, can tell you a lot about what is wrong by looking at the numbers after the word, "STOP." For example, you will see a code such as 000X000000. These numbers identify what is wrong, and you can check online to see what the stop code means (see Resources). However, these blue screens are most often because of bad device drivers, hardware elements which have gone bad or software that has been installed. You will need to boot in Safe Mode, and then, by process of elimination, remove and replace suspect drivers or hardware, to determine what is causing the freeze. Think back to the last thing you did before the freezes began. Installing a new device, dropping the computer or installing new software are all common causes for frequent freezing.
Methods of Keeping a Computer from Freezing
Keep your computer running by cleaning the hard drive of temporary files, defragmenting the hard drive it on a regular basis and being careful to only install necessary programs. While it is fine to install new programs, be aware that some programs may use up the CPU or memory uncontrollably. Be particularly wary of beta programs, which are still being tested. While in the testing stage, they may be a cause of frequent freezes. Use the System Restore feature to remove the effects of a harmful program. It is a safety net in case you cannot remove a program using the Add/Remove Programs feature in the Control Panel. Viruses and malware will cause a computer to act strangely or to freeze up completely. To avoid this, use virus and malware checker programs, and keep both those and Windows updated. If you dropped your computer, have the hardware checked; problems won't always manifest themselves until later.