with video cards as long as there the same slot type. http://www.kids-online.net/learn/click/details/agp.html
old video cards slot. http://forums.techguy.org/attachments/178086d1283142567/howtoselectbus.jpg
newer pci slot.
newer pci 3.0 cards will work in older motherboards as long as your power supply has the wattage for the gpu and there no bios issues. (not all vendor cards work in all mb). google the make and model of your motherboard make sure there no hidden issues with the bios or chip-sets and newer video cards.