Tx guys.
Checked the bios updates,conflicts,
ports, heat sensor.... you name it!!
Then after taking the box apart bit by bloody
bit, we discovered the problem....
A faulty power supply. ghnnnnGrrr!
Replaced it - and its now been up and running
without any hassles for close on four days.
Thanks again for the help.
PS. Seems the sound/printer port was the last
straw - which pulled the power supply over
the brink!
Strange!!!!!