There are two types of maintenance that can be applied to a computer:
Preventive Maintenance: He applied to a PC in order to avoid future mistakes and technical problems, such as: Find and remove viruses from your hard drive, find and correct errors in the physical and logical disk, disk defrag, clean up the motherboard and other cards to avoid technical problems due to dust, etc..
Corrective Maintenance: One who is oriented to diagnosis and repair of equipment when a technical problem.
When we maintain a computer, we must first determine what is the time of use and delay of computer technology. The services on very old computers is more expensive and therefore difficult to get the spare parts.
Then, evaluate the physical conditions of the computer. An ancient or modern computer can not be installed on site very closed or have books and materials on top that not allow to dissipate the heat generated on the motherboard. (Despite being cooler on the inside). Not necessarily must be in a room with air conditioning but in a cool place.
As for electricity, there are users that have hydro-pneumatic pumps, air conditioners, and a number of electrical equipment that consume much energy at boot time, is there just as the hard disk of the computer is suffering because it is very sensitive to electric failures and every time the fridge turns on, there is a low amperage in the electrical system throughout the house and consequently on the PC. Since this fluctuation power, hard drives trend to suffer much damage.
We can begin to look for and remove informative viruses with a good antivirus.
Find and delete temporary files on your computer (*. TMP) that occupy space and trend to crash the computer.
Also look for files with the CHK, if your disk starts to make files of this nature, it is likely that we are in the presence of a future damaged disk, because these files are usually lost fragments of other files that are not well saved or maybe it was lost because the computer turned off unexpectedly, or data recovered from a bad sector on your hard disk.
If the computer has more than 2 years that the operating system was installing, do a Back Up of all important files to the user and format the hard disk, and reinstall all programs. Will see fast improvement.