There should be a button on the keyboard that has a symbol on it that looks like wifi waves. I believe it's either on the F10 or F12 key. It will be glowing red / orange if it's disabled. Press it again and it should glow white, which means it's enabled.
If that doesn't fix the problem, try enabling it via Device Manager. Click on the Windows start button and search in "Device Manager." Click on it, and go to "Network Adapters." Enable anything that isn't enabled (Right click on the device you want to enable and click "Enable")
Hope I could help