Wi-Fi problem "No hardware installed" - MacBook Pro mid 2009, Yosemite

Hello,

My Wi-Fi in no longer working and the systems says "Wi-Fi: No hardware installed" (See screenshot)

I tried different solutions and ultimately deleted the Wi-Fi interface in the Network panel within System Preferences, as suggested in a support forum, with the intention to add it back once the computer rebooted. Unfortunately now I can't even add the Wi-Fi back as an interface...

The systems lists "Bluetooth PAN", "FireWire", "Ethernet", "Bluetooth DUN", "VPN", "PPPoE" and "6 to 4", BUT NO WI-FI (See screenshot).

How can I get my Wi-Fi connection back?

Thanks for your help and support!

Best regards,

Olivier