The Z906 is a stand-alone sound system. Your PC does not recognise the speakers per se, but only the type of cable you wire it with.

If you use the 3x 3.5mm plugs, Windows will suggest a 5.1 system and you can set certain parameters yourself.

The Z906 is DTS/Dolby capable if you connect it via an optical cable and has its own software that decodes and addresses the individual channels. But then you can't do much yourself in Windows because the original bitstream goes directly to the speakers.

The Z906 always allows you to change the centre, rear and sub levels. There are also predefined presets for which channels you want to use (2.1, 4.1, 3D surround).

with the information proposed it is not possible to give an answer, you need to know how it is You need to know how the Z906 is connected to the PC (e.g. the three direct 6-channel jacks in the PC or stereo or optical RCA), which sound card is in the PC (e.g. Realtek HD or others), have you run an audio test to see if all the speakers are working, however you can also adjust the subwoofer level via the remote control with the LEVEL button and the + - buttons, you can run the test on the remote control by holding down the INPUT button for 5 seconds you should hear a hissing sound in sequence from the speakers, I hope I've been helpful.