Directory Opus compatibility with Windows XP 64 bit

I'm resurrecting an old PC to run one specific program that requires Win XP. When I try to install Directory Opus I receive an error message that 'The OS requirements for the installation have not been met'.
This PC has 64 bit Windows XP with SP1, 8 GB RAM, 120 GB HDD and 3.2 GHz processor. I'm told SP2 was the latest available for XP 64 bit.
Windows compatibility mode is disabled.
I've tried both DO version 12.20 and version 11. Is DO able to run on such a machine, and if so what am I doing wrong?
Thank you. Robert, SE Australia

Solved. I updated Win XP to SP2 and the install proceeded without problems. Don't you just leave these self-answering support requests?