Final answer:
To resolve the issue with the unrecognized integrated sound card, check and enable it in BIOS settings, examine Device Manager for hardware conflicts, ensure proper drivers are installed, and consider a system restore or contacting support.
Step-by-step explanation:
When the integrated sound card is not recognized after removing a PCI sound card, you'll need to perform a few troubleshooting steps. Firstly, ensure that the integrated sound card is enabled in the BIOS settings. You might need to restart your computer and press a specific key (such as F2, Del, or F10) to enter the BIOS setup. Once there, look for audio settings and ensure the onboard audio is enabled.
Next, check for hardware conflicts or issues in Device Manager, even though the sound card is not listed. View hidden devices to ensure there are no conflicts with the sound card's drivers. If necessary, install the correct drivers for your motherboard's audio chipset from the manufacturer's website.
If the problem persists, consider performing a system restore to a point when the sound was working, or consult the motherboard manual for troubleshooting tips, or contact customer support for your motherboard.