So on my friend's computer, his RJ45 jack stopped working. I thought maybe it got shut off in the BIOS, even though it just stopped working while using the computer. Its not the cord it self as when he plugs it into his xbox 360 he geting connectivity. When he tries a different ethernet cord he still doesn't get anything. So he brought it to my house, and plugged it in here still nothing. I really don't know what to do at all.

Do the orange and green lights on the RJ45 work? i.e do they flash or are they solid?

Have you tried disabling and enabling the Ethernet adapter?
Network Connections -> Right-click on Local Area Connection -> Disable. Then do the same and select enable.

If that doesn't work, you can also remove the driver and re-install it.
1. Download the latest driver for the Ethernet adapter from the manufacturer's website.
2. Right-click My Computer -> Manage. Select the Ethernet card from under Network Adapters and un-install the driver.
3. Re-boot your machine and run the setup file for the driver you previously downloaded.
(You can also try running Windows update after rebooting and it will automatically find a driver for you, but I personally don't like doing that.)

Ill try that right away, but no the lights don't come on. Also its just the ethernet port that came with the mobo, not like on a pci card.

Ok, then you need to download the latest motherboard drivers from the manufacturer's website.

and if that doesn't work ,then i suggest going out and buying and installing a pci nic card