The HP Pro Tower Zhan 99 G9 desktop PC is a high-performance computer that can support various components, including a separate sound card. A sound card can be added to enhance the audio capabilities of the computer, allowing for better sound quality when using headphones, speakers, or other audio devices. To determine if your HP Pro Tower Zhan 99 G9 desktop PC can accommodate a separate sound card, you may want to check the computer's specifications or contact the manufacturer for detailed information. If your computer does not have a built-in sound card, you can look for an external sound card that meets your needs and connects to the computer via USB, PCIe, or another appropriate interface. When choosing a separate sound card, it's important to consider factors such as the card's compatibility with your operating system, the number of channels it supports, the maximum number of simultaneous connections it can handle, and other specific features that are important to you. It's also a good idea to check reviews and ratings of the sound card models that interest you to ensure that they meet your requirements and provide the desired audio performance.