Is a pci express x16 video card compatible with my pci express slot?

I am planning to upgrade my computers video card because its original is dying out. So i found one online but it is a pci express x16 card and has a ddr2/gddr3 memory interface. And my computers video card slot is a pci express and the original card is a ddr memory interface. So I want to know if the card I am wanting to purchase will work or not with my computer?|||Yap, it should work.