Anyway, I followed the instructions I found in a thread in Logitech's forum:
Make sure that the headset's microphone plug is inserted into the pink port of your sound card. Verify if it is plugged all the way in.
Check if your computer has front ports for headphones and microphone. Test if the headset works with those ports.
Open the Device Manager (Start > Control Panel > System and Security > System > Device Manager)
Expand "Sound, Video and Game Controllers". Look for your sound card manufacturer name under the list (e.g.,SoundMax Integrated Digital Audio, Realtek High Definition Audio, etc.). Right click and choose "Update Software Drivers".
Follow the instruction prompts to proceed with the update.