A surge protector or also known as a surge suppressor is an appliance or device that is designed to protect electrical equipment and appliances from damaging voltage spikes. Surge protection attempts to act as a limiter for the voltage that is supplied to an electric device by blocking or shorting the excessive amount of voltage (above the safe threshold) to a safe ground.
It is recommended that you should preferably make use of good quality surge protection with your electrical equipment like a computer. These type of devices are filled with voltage-sensitive components that can be damaged and broken very easily when a power surge occurs. It is always a good idea to make use of a surge protector for any other high-end electronic equipment, such as sound equipment.
A general wide spread misconception regarding the abilities of surge protection is that it will completely and fully protect all of your electronics from any form of excess power. Your surge protector may have gone bad without showing any signs of damage a surge can simply be way too big, the surge protection may fail to protect your electrical equipment from the sudden increase in electrical current.
If your surge protection is really old, and you are unsure if it is still in working order, it is probably not protecting you as you might expect and you should have it checked out by a professional. If you are aware that your surge protector have taken a big hit, you should probably call a professional to assess and possibly replace the system. Otherwise, a good rule of thumb is to get it checked out about every two years.