nc6400 strange power issue

Hi guys
I have a really strange power issue and cannot loaclize the problem and i was hoping that someone could assist.

I have a HP Compaq nc6400 that was running 100% on the processor even on a fresh xp install. i tried install linux mandriva and when it got to the time settings it would freeze and not go any further unless i unplug the power supply! also during an XP install it would seem to “freeze” however unplugging the power would start the install again! Anytime that the power supply is connected it is running the processor at 100% It is the origonal power supply and i have not changed any hardware in the machine. IT also seems that the battert will not charge to 100% either.

Any ideas?