You dont need to do nothing before installing the card... Expect maybe unplug the pc...
Aslo you may need to gointo the Bios, Press F1 on reboot...And as i dont know your exact motherboard you will have to look around..usually in advanced though... And it will say video.. make sure it say's (if your using a pci card) PCI, or agp etc..
If you can spend 30 more bucks you get a vid card that can actually play doom 3...
http://www.newegg.com/OldVersion/app...102-510&depa=1
Its agp, there much better card's...
But again if you put in the pci card just put it in and turn the pc on and it will come with a disc for drivers once you reboot install the drivers and your ready to go