In place - sound card (left) and graphics card (center) in white PCI slots. There is room for a network card, if required.

Nowadays, graphics cards are usually fitted in the AGP slots provided specifically for this purpose. These are brown in color, in contrast to the PCI slots, and are generally located in the center of the motherboard. PCI graphics cards are rarely used. Now, select a PCI slot for each of your other plug-in cards, including the sound card. Before fitting an expansion card, remove the appropriate slot insert from the back panel of the case (or of the motherboard tray). As a rule, you need to undo a screw to do this, although sometimes convenient plastic clips are used. The insert may also form part of the back panel.
Choosing a location for a PCI card will not usually be a problem on a simple system. In our experience, however, selecting an appropriate PCI slot can sometimes be problematic with some brands of motherboard. For example, IRQs can be reserved twice or even three times over. Resource conflicts can make it difficult for the operating system and motherboard to work together properly. This can often be solved by moving the offending PCI card to another slot or by manually reassigning IRQs. The other reason is more practical. If you see a large heat sink on a plug-in card, perhaps even with a fan on top, the chip underneath will be producing a lot of heat that has to be removed. There is only one reason we did not fit the sound card next to the graphics card: we wanted to keep some space between the cards in order to prevent heat buildup.