Inspiron 5675, network issue

Hello,

I have Dell Inspiron 5675 and wifi and Ethernet options disappeared. So i cannot use internet on PC. tried a lot of things but nothing worked. I installed drivers. It says succesful instaliation but when I go to device manager and choose it says no driver installed for this device. Also i can't find it in BIOS. I mean no LAN or simia otions there. Anyone knoes ehat could be a problem and how to fix it? I also bought wifi usb adapter but it doesn't work either. I just don't understand why. I would be grateful for any advices.