What is preventative maintenance for computers?

Preventive maintenance on computers is to ensure the smooth running of system applications by ensuring the system is free of malware's, virus and clocking with file fragmentations. It also involves ensuring the computer circuits is free of dirt and protection of the electronic circuits from over voltages.

Proper power source, regularly cleaning,proper installation desk / table cool dry atmosphere  

preventative maintenance is having an up-to-date anti-virus scanner. An anti-virus program can usually be scheduled to run in the background when your computer is not being used. Consult your user manual to learn the process for updating virus definitions, the list of viruses the software uses to recognize problems. Software can be set to update definitions regularly. It only takes a few seconds for most programs to update. Scanning your computer can take longer but should be allowed to proceed at least once every week.

Checked and run for removed the bad sector using the working procedure by recommended your department and make run faster and software updated.

And shall be carried out at any time as necessary to protect the device from dust, dust, rust, noise, heat and other sources of fault such as change in frequency / voltage of the current and magnetism to prevent the occurrence of accidents or reduce the probability of occurrence.