Dude, those CPUs have maximum temp of 72C. Your thread is dated 2005! You probabably damaged those CPUs beyond repair if they were idling at 70C!!! Since you wrote XP could not be installed and kept crashing midway, I assume the problem is either with:
Moreover, you have problems with your hard drives in another thread.
So why don't you do proper troubleshooting and see what happens instead of running through RMAs, board replacements and all?
Boot from CD, run memtest86 post what happens.