Installing 2 graphics cards

[Alphatonic]

SYSTEM
Windows XP sp2
motherboard:ASUS cuv4x-e
Pentium III
640mb SDRAM
120 gig HD

Im trying to install 2 graphics cards on the same PC so I can have dual monitors. I dont want to go buy a dual monitor card because I have quite a few single monitor cards already.
I have PCI and AGP graphics cards to use.
I started with NIVIDIAGE force MX4000 then just added another one. Tried a AGP and a PCI, neither worked. They were recognized but an error occurs everytime with the newely added one.

any tips???

Thank you

[upgrader]

I think the only way to have 2 graphics cards in one system is to use a dual technology like Nvidia SLI and ATI Crossfire, but one of the tech heads should be able to clear this up for me

[GaRHaR]

Upgrader is correct.

You can only get dual video cards in a system if they are aware of each other.

most video cards of old are not aware of each other - and the AGP will always try and take the leadership as it's an Advanced Graphics Port.