Michael
I then took out one of the existing boards from another slot, put it into one of the spare slots and then fitted the Boltek into the slot that was now vacant, it then worked perfectly.
Thanks for the advice. Unfortunatly, both our computers are Shuttle (small form factor) and each only have one slot. As thay both run 24/7 and are connected, if all else fails it may be worth trying the boltek in the other computer. Thanks again
Bob