My cpu is heated up,knowing that the system didn't start yet.. so the system is opening the safe mode and start windows normally page,so whatever I choose,the system restarts after it loads to the page where the windows is starting
,then it restarts.

They will heat up and shut down if the fan is broke, or clogged with lint.

Indeed, I would also say it's the overheat protection built into the computer.

Hey thanks for the help guys... bt the problem was that the startup file in the windows has been deleted:S:S

What is :S:S?
What Version Windows?
TRy System Restore?
Can you describe more what happens? Safe Mode?
PC Review - Startup Files (http://www.pcreview.co.uk/startup/)

:S :S is like that a sad face... I have XP sp2... well I made a format so everythg is OK now...