nvidia geoforce 2 card problems

Hi,
Recently purchased a nvidia geoforce 2 card. I am running
WinXp on a 512mB 500Mhz system. Having installed the card
& loaded the drivers, the computer sees two monitors. The
default on the onboard Intel 810 graphics chip and the
additional Geoforce 2. The displays on both montors are
different. I have tried to switch off the onboard graphics
chip through the Bios, and make the Geoforce the Main
deafult graphics card. This only results in a failure to
boot up. The card has to be then removed and I have to go
back into the Bios to switch the Intel graphics chip back
on. It appears that the two cards work ok side by side -
albeit with a longer boot up and having sometimes to swap
between screens to carry out my work.
Any help or advice would be appreciated. Please accept my
thanks in advance.