Older computers use volatile RAM supported by a battery to store boot data. These batteries often last for many years. The result is that they become a forgotten component and it is only when the computer starts doing strange things, that owners even realise this component exists. So if your computer starts to behave strangely at switch on, then look to see if a battery supported CMOS RAM might be the problem. This lithium battery is very common in CMOS memory support and once replaced, the computer will return to its normal reliable self. Amazon are able to supply these batteries quickly and cheaply.