I would install the card first, so that your new install of XP does
not install your old graphics set up, which you will then have to
uninstall to install your new card. (and just might leave little bits
of the old set up as well)
If you are going to install XP, please do so as a fresh install, and
not an "upgrade"... Backup whatever you want to keep from your present
set-up, and install your XP clean.. You will be happier in the long
run.
If you are switching over from an "intergrated" graphics card, make
sure you disable your onboard graphics in the computers BIOS, before
you install the card, or you will have problems. Some BIOS also have a
switch for AGP and PCI graphics, make sure to set that switch
correctly for your new card.
My .02 cents.
JM