I am starting by assuming you have a D8445HV MB ?
Did you find this document? http://downloadmirror.intel.com/15332/eng/D845HV_TechProdSpec.pdf
I dont see any reference to a jumper, but these is a BIOS set-up option to select ECC if you DIMMs all support ECC
Sorry for such a gross error. The motherboard is an Intel D845HV. I have looked in the bios description of the setting for ECC/non-ECC, and the ECC is the default setting. I have tried to set the 'defaults' but it still will not accept the ECC memory.