Excess heat will cause many problems. You can check to make sure the cooling fans are running. One is in the Power supply which you should be able to see without taking the cover off. One will be on the CPU itself. You will need to remove the cover on the computer case to see this. Turn off the computer, take the cover off, turn the computer back on and take a look at the CPU fan. If they are not running or are running slowly or sporatically, they would need to be replaced. Do not leave the cover off for long periods of time as it is part of the cooling system.
Also while you are in there, it is a good idea to clean out the dust that has accumulated. Make sure you are careful not to induce any static electricity in doing this. I usually use a can of compressed air and carefully blow out the dust. If a vacuum is used make sure you can ground the wand so it does not build up static electricity.
If there are actually components "leaking", you need to take the computer to a fix'em-up-shop. If it is old, you may want to consider that it may be time for a new computer.
My machine is AMD ATHLON Windows XP based.I have AVG ANTIVIRUS free edition and spybot search & destroy installed.Also I have spyware doctor installed.The system suddenly hangs or screen goes blank.Sometimes it shuts down itself.When I opened my cpu I found some capacitors on mother board leaky. Could this problem be related to this?Also my machine does not enter the standby mode? Any help please.