Hi Paul
Firstly Everest is no longer updated. I would try
PC Wizard - it agrees with readings produced by CoreTemp but CT does not support the P4. I used to have a Pres-
Hot P4 - 70C was fairly normal with a reasonable load - 75C under heavy load was not uncommon. The P4 will throttle back before any damage is done, slowing down your PC until the temps drop.
I know you can buy
cooling pads for a laptop but I've no idea on their effectiveness.
Before I moved to SMP, I ran the normal client somewhere around 70-80% usage, I think.
Hope that helps a bit - one of the hardware guys will likely be able to give you more info.