yes spot on,funny coincedence,im going to buy a nvidia geforce 7600gs tommorow so this method is fresh in my mind
some users may uninstall the driver for the old card first,then change the card,boot up and then install the new driver for the new card,theres many ways you can do this,but they all are around the same principle
if you are changing to another brand of manufacturer(i.e nvidia to A.T.I)then you may want to run a utility called "driver cleaner" avalible from http://www.drivercleaner.net/
this will scan your system and delete any old files belonging to your previous card(dll,s ,temporary files)as the driver uninstall dosent allways remove every single file,and sometimes(only sometimes)old driver files can cause conflicts and could affect the quality of your new driver installation
if your using the same type of card,dont use your existing drivers,although the drivers are unified(they work with all cards)its allways best to remove the old drivers and install a fresh set of drivers
just for your reference heres all the main drivers download site links..........................
nvidia...http://www.nvidia.com/content/drivers/drivers.asp
a.t.i...https://support.ati.com/ics/support/default.asp?deptID=894&task=knowledge&folderID=27
also certain cards require a power supply,so make sure your power supply is adequate,a 400watt p.s.u should be fine for most cards
if your not sure and require any more advice just let me know
good luck mate!