hd4850 512mb

ok im think about get the hd4850 512mb from this website http://fxvideocards.com/Sapphire-HD-Radeon-4850-p-16386... also has anyone bought from this site it has a good price also i want to know if it will fit in my gateway gm5067h case in my pci express x16 slot. will it matter if i have an intergrated graphics is there way like put this card in and it disables my nividia 6100 gpu. plus i need help because no one in my family know **** about computers im only 13

p.s quick response (also will this card play crysis on high with 1gb maybe 2gb ram amd atholon 64x 2.2ghz in windows xp)