You will need to install network support - Samba or CIFS - but I don't know the details. Then you will need to configure your PC to share the drive.
If all you are doing is wanting to stream content from the PC, you can do that without the custom facilities if you set up a DLNA server on the PC - eg XBMC - but the Humax has a bug that limits streaming to 4GB per file.
When you see your PC's name under "network" that is actually what's happening - the Humax is searching for a DLNA service. Mounting drives by Samba/CIFS will make them available as if they are USB drives and you will need to access them accordingly.