At firtst it sounded like a driver issue, which means you would need to get the proper driver...
However, since you don't see any device , it means either : 1.
the sound card device is accidentally disabled in the BIOS (press F1/F2/F10/DEL key at computer startup to enter BIOS, the key depends on the manufacturer). Look for Onboard Audio->enable/disable. 2.
The new I/O card you installed is conflicting with the sound card I/O. Try removing the PCI card and see if the sound card reappears. If it does, install the PCI card in a different PCI slot. 3.
Some other hardware installation is conflicting with your sound card I/O settings. Try removing any external cards or new devices from your system and see if your sound card appears again in Device Manager, with yellow mark or now. 4.
Another installation has messed up with your Windows Registry and I/O settings, download ccleaner
, clean up your pc and registry and see if it helps. 5.
In device manager, expand System Devices and look there for questionmarks/exclamation marks too. Try uninstalling the devices PCI DEVICE and OTHER PCI BRIDGE DEVICE if they appear with yellow marks. Note: Don't worry about WAN Miniport (SSTP)..it's normal.