PCI Serial Port driver not installed (Windows 7 64-bit)

Ever since I installed Windows 7 (64-bit), the Device Manager shows under Other Devices / PCI Serial Port / Properties / "The drivers for this device are not installed. (Code 28)".

I've update the drivers for my main-board (ALiveNF6G-GLAN) with the files from here and for my graphics card (GeForce 6150SE) and chip-set (nForce 430) (v15.49) from here, but the PCI Serial Port driver is still reported as not installed.

Deleting the device (and letting Windows re-detect it) doesn't work either.

I'm really frustrated by this problem because I suspect it might be the cause the Windows doesn't enter Sleep/Hibernate mode correctly (e.g., the CPU fan keeps running).

Any help would be greatly appreciated!

PS. Please ignore the system specs below this post. Those are for my PC. This problem is on my wife's PC.

Taka a look at page 43 of the manual, how to disable Serial Port.
You can download the manual from your link.

The serial port was already deactivated in the BIOS. Just to test, I activated it and gave it the first-listed port number. Windows 7 Device Manager still shows the same error ("The drivers for this device are not installed. (Code 28)"). :-(

Any other suggestions, please?