FirePro 2450 is not supported under Windows 10. You will have the generic driver supplied by the OS for FirePro 2450
Actually, here is the answer. This H.P. was originally shipped, as were many I suspect,with Windows 8 installed or maybe even Windows 7. In that original configuration, H.P. installed a security system in the BIOS that recognized and required the original configuration and would not allow changes to prevent root kits and other malicious activity from impacting the hardware. Shortly after I posted this question I did find an article on the HP Customer Support site that provided the solution. The link is http://support.hp.com/us-en/document/c03653200, please see that document for all the details.
Very briefly, what you will need to do is return the computer to it's original state in terms of removing the add-in video card (activates the built in video adapter) and in my case I had to locate and use the original equipment keyboard. My after market keyboard did not become active soon enough in the boot up to 'grab' the BIOS entry.
Once in the BIOS, go to the security menu and enter the Secure Boot Configuration setup. Pass the warning and then disable the Secure Boot and Enable Legacy Support.. Save and reboot. There is then a Boot mode change message requiring the entry of a four digit code and the computer will finish booting up. You can close down, re-install the AMD video card and you will, probably, be up and running. My ATI FirePro 2450 works great. I don't know about the software for it, but I have access to all four ports and I have three monitors running. Two are strictly DVI; one is a very old Princeton VersaSync, and one a two year old Samsung 24 inch (S24D230BL/ZA). The third is a newer Samsung 24 inch S24D300 which actually had to have and adapter added to the DVI to fit its HDMI input. I used a Rocket Fish Model RF-G1173 because that's what Best Buy had and I was anxious to get up and running.
I'd put up a fourth monitor, but I don't have the need or the desktop space. If I run in to a bargain, maybe I'll hang one off the wall. Thanks,for the suggestions.
I hope this answers some questions for other folks.