My laptop shuts off repeatedly / sometimes/ and can not start ON as easily as before , why??

hello guys thanks for your quick reply for my privious question.as i sayed my laptop shuts off from the main electrical supply by itself while im working or installing softwares.( sometimes). and it is also can not start my operating syatem when i press power swich ON/ OFF...if the windows starts working , it stays a little bit long without shuting down.i reinstalled new windows 3 times and scanned my system disck several times by using deferent anti virous like ANTI VIR, AVAST ,AND AVG anti virous. but nothing can be solved. bytheway i used to had on my laptopes deferent softwares like TUNEUP 2008, CCcleaner, Speed it UP 4 FREE, anty spyware begone, AVG anti spyware, AVG anti virous, and some SCRIPTS of Messenger 8.5 VERSION .

PLZ send me ur respons as much as you can. thanks alot and GOD may Bless u ! (( but thanks God that my laptope still do not shuts off untill i write this message that means almost morthan half an hour lol)

My laptop shuts off repeatedly / sometimes/ and can not start ON as easily as before , why??pc security

More like a hardware overheating problem to me, since you have done so much. Try to add a cooling pad under your laptop. It may be the overheating problem. Another thing to do, if you take your battery out of the place, the heat will not raise that fast. You can also clean up the ventilation of your laptop. Next step will be the RAM check, bad RAM location/s will cause the shut down, too.