Pc getting shut down after 10 minutes

Hello,
i am using window 7. i have pc with 2gb ram 500gb hard disk dual core processor
when i on the pc . it show me that pentium processor installed & you have to restart now. when i restart this problem occur next time .if i don't restart then after 10 minutes it will automaticly go in position that pc power supply is on but hard disk light (that is red) will off. also moniter not get any signal .
please suggest me what i do?