This machine is a Japanese only market.... meaning you cannot find a driver page in English. If your Japanese is good you can go to the Japan NEC website and download drivers.
The best bet would be to give me the hardware id string found in Device Manager. Open the Device Manager and double click on the item in question, you should get its properties.
Note: (it may be listed under "Unknown Devices" if no driver has been installed)
On the properties page, please direct yourself to the Details tab.
Make sure its set to "Device Instance ID" and copy/paste the ID string for us.
For ethernet, modem, audio, video cards, etc. it usually starts something like "PCI\VEN_"
or if it's a USB device, "USB\VID_". Top/First line of text only.