There may be a hardware button using the FN key that enables and disables the onboard NIC.
Also check and make sure the NIC drivers are functioning properly by going into the hardware manager and opening the properties of the device. If it says this device is working properly, then it may be a problem with your cable.
Do you have another machine to test that cable with?

as WizKid009 said, test your cable on another computer, although, there are various ways to disable your wireless, such as: laptops normaly carry a on/off button for that, you can disable it on the computer, or use the FN keys. It can also be a problem with your rj45 port.

Go to:
Start->Control Panel->Network and Internet Connections ->Network Connections
Then right click on your card that uses the hardwire (not the wireless card), and choose "enable". You may want to disable the wireless card if you did not disable it this way (i see you disabled wireless, but you did not specify how).

If that still doesn't work, you could try a repair. Just go to the place I mentioned above and right click and click "repair".

If that doesn't work, take the cable out of the computer. Does the computer tell you that a network cable is unplugged (it'll say on your start menu)? If it does, then your network card is probably working fine. Check your router or internet connection. If it does NOT tell you that an internet cable is unplugged, then there may be something wrong with your card or something else disabling it. A lot of ppl here mentioned using the FN keys. That is a good start.