"can anyone tell me why I should be getting a message CPU temperatuee is to high when I start up"
Because the CPU temperature is too high, I would imagine.
You need to look into the processor cooling system - is the fan going? - at the correctspeed? Can you look in the BIOS at the PC Health section - does it show the temperature, or if the fans are going, and at what speed?
Can you tell us some more about your system please - age, processor type, speed ect.
I suggest you look inside pronto, and see if there's anything really obvious.