Driver Cleaner
link,.
Short guide is to remove your old drivers via Control panel in add/remove program icon,reboot into safe mode run Driver Cleaner(don`t forget to install it,also full instructions for Driver Cleaner are in the readme file once you`ve downloaded it) also if Windows detects new hardware while booting up in safe mode hit the cancel button,run DriverCleaner for" Nvidia" at desktop in safe mode,you also have the option to run cab cleaner for XP SP1(service pack 1) which can be found in tools menu of Driver Cleaner,anyway once you`ve run Driver cleaner and cleaned any remaining old drivers files close the PC down,switch out your old card and install your new video card,boot up to normal desktop,if windows detects new hardware hit cancel,once at desktop install the new 4.2 ATi drivers.
I recommend you download ATI drivers( single setup installation is best,listed as high speed DSL/Cable) from
here and have them ready on your PC for install.The ones on CD that come with your sapphire are normally out of date.
That`s the way I did it going from my GF2 Ti to Sapphire 9700NP.
Btw don`t forget to connect the power lead to the 9800 Pro card.