Hi there blade runner, welcome to the forums proper.
Try to use the
PSU from your other 8KHA+ setup, and ensure that the JCK1 jumper is set to the correct position in each case (1-2 for duron and 2-3 for the XP's).
Try to see if theere is any trace damage around the zif socket that may have been caused by a screwdriver whilst installing the
CPU cooler (there are tracks there between the northbridge and dimms - a possible cause of a C1 error).
Other than that it is possible that the mainboard may be at fault. In which case please do contact your branch office for further assistance in this case.