I think you haven't installed proper driver
for the network hardware component.
1. Find out what network device do you have? company, model etc.
2. Install appropriate driver, that means it should work in your current OS.
3. If your network driver manufacturer is computer manufacturer then visit manufacturer's website and you should be able to download appropriate driver.
I had same problem with my sony vaio wireless (My wired connection was working fine), I downloaded a wire less updated driver from sony website and it worked after installing it.
Your problem sounds to be software related. It should be solved easily, you just need to find out right driver setup.exe for your hardware which is compatible with your current OS.
All the best