AGP plus PCI video problem

[md64]

I used to run a NVidea GeForce MX4000 dual monitor AGP card happily alongside a NVidea GeForce2 MX PCI to get triple monitor output no problem. The single monitor PCI was recognised first and took over all the POST screens and what have you, then as Windows loaded the AGP monitors kicked in and I used UltraMon to control it all.
Now Ive got a new base unit and for some reason it just wont work anymore. Same two cards, same three monitors, but now if I install the PCI card I get the POST screens and then the monitor just goes blank - the monitor light stays steady to say its getting input, and I can hear Windows running no problem, I just cant see it! If I take the PCI card out again then Windows happily accepts the AGP pair instead. If I take the AGP card out then the PCI works properly. Ive tried booting into Safe Mode with the PCI installed and that works okay, but as soon as it reboots I lose video straight after POST again
I cant fathom it out - nothing is different between the two setups except of course the motherboard (its an ASRock P4VM8 in case that helps, and my old system was an antique Compaq Pressario). Both running WinXP SP2, both with a gig of RAM althougth the old setup was a 1.3 Athlon and now I have a 3.0 Pentium. Anyone got any ideas on how I can enable this again - I used to very much enjoy the triple setup and I feel hard done by with just two!

[skold]

go into your bios and look for an option labelled something like 'init display first' and make sure it's set to pci or agp (try changing it from whatever it is now)

like this: