Expansion slots are typically located on the back lower half of the computer case. Expansion slots are the place where your PCI and AGP cards pertrude from. There are bit and bit PCI expansion slots. Sadly, without opening the case, there's no way to determine what type of slots are present on your PC's. Upgraders and budding builders alike know that a PC chassis is not just a to clamp a PCI or PCI Express card into the case's expansion slots.